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Hydrolysis and Transformation of Grape Glycosidically Bound Volatile Compounds during Fermentation with Three Saccharomyces Yeast Strains
Abstract
The ability of three Saccharomyces wine yeasts (S. cerevisiae AWRI 838, S. cerevisiae AWRI 1537, and S. bayanus AWRI 1375) to liberate volatile compounds from sugar-bound aroma precursors was investigated using synthetic and grape glycosides under different experimental conditions. In model systems involving the incubation of yeast cells with either synthetic or grape-derived glycosides under conditions more favorable for glycosidase activities and less favorable for acid-catalyzed hydrolysis (pH 5.0 and 30 degrees C), all yeast strains studied proved to be capable of hydrolyzing glycosides, with S. bayanus AWRI 1375 displaying greater hydrolytic activity than S. cerevisiae AWRI 838 and AWRI 1537. During the fermentation of a chemically defined grape juice-like medium containing glycosidic precursors extracted from Vitis vinifera cv. White Frontignac (synonym Muscat à Petit Grains Blanc), all yeasts promoted a significant hydrolysis of different precursors, which varied according to the chemical structures of both the sugar and the aglycon moieties, as determined by GC-MS analysis of trifluoroacetylated derivatives. Hydrolysis of the White Frontignac derived glycosidic precursors during fermentation resulted in the release of monoterepene alcohols, terpene oxides, terpene diols, and 3-oxo-alpha-ionol, demonstrating the significant potential of these yeast strains to contribute to wine varietal volatile composition during alcoholic fermentation.
... The hydrolysis of bound flavour precursors and subsequent release of volatile compounds have been of interest to wine for decades [6][7][8][9], with studies investigating extraction for the purposes of quantification or in vitro evaluation [10][11][12] and application of exogenous grape or wine-derived precursors to modulate flavour outcomes [13][14][15]. More recently, attention has focused on the flavour precursor potential in grape marc [16][17][18]. ...
... Studies on the hydrolysis of glycosides to yield flavour have largely focussed on quantitation of the volatiles derived from aglycone liberation to determine the outcome [14,[22][23][24][25]. In some instances, the glycosides themselves have been monitored before and after a particular winemaking stage or period of storage [13,17]. In the case of Ugliano et al. (2006), fermentation with different yeasts in the presence of a glycosidic mixture isolated from grape juice produced a decline in total glycosides. ...
... In some instances, the glycosides themselves have been monitored before and after a particular winemaking stage or period of storage [13,17]. In the case of Ugliano et al. (2006), fermentation with different yeasts in the presence of a glycosidic mixture isolated from grape juice produced a decline in total glycosides. Additionally, every individual glycoside monitored declined, significantly or otherwise, which was also the case in their non-inoculated control. ...
The winemaking by-product grape marc (syn. pomace) contains significant quantities of latent flavour in the form of flavour precursors which can be extracted and used to modulate the volatile composition of wine via chemical hydrolysis. Varietal differences in grapes are widely known with respect to their monoterpene content, and this work aimed to extend this knowledge into differences due to cultivar in volatiles derived from marc precursors following wine-like storage conditions. Marc extracts were produced from floral and non-floral grape lots on a laboratory-scale and from Muscat Gordo Blanco marc on a winery -scale, added to a base white wine for storage over five to six months, before being assessed using a newly developed membrane-assisted solvent extraction gas chromatography-mass spectrometry (GC-MS) method. The geraniol glucoside content of the marc extracts was higher than that of juices produced from each grape lot. In all wines with added marc extract from a floral variety, geraniol glucoside concentration increased by around 150-200%, with increases also observed for non-floral varieties. The relative volatile profile from extracts of the floral varieties was similar but had varied absolute concentrations. In summary, while varietally pure extracts would provide the greatest control over flavour outcomes when used in winemaking, aggregated marc parcels from floral cultivars may provide a mechanism to simplify the production logistics of latent flavour extracts for use in the wine sector.
... 2,8,9 The biochemical release of aglycone from the glycoconjugated precursors can occur during alcoholic fermentation (AF). 10 In this case, the hydrolysis is catalyzed by yeast glycosidase enzymes 10 located in the periplasmic space. 11 Biotransformation of terpenes present in free forms in the grapes or released from glyosidic precursors can also occur. ...
... 2,8,9 The biochemical release of aglycone from the glycoconjugated precursors can occur during alcoholic fermentation (AF). 10 In this case, the hydrolysis is catalyzed by yeast glycosidase enzymes 10 located in the periplasmic space. 11 Biotransformation of terpenes present in free forms in the grapes or released from glyosidic precursors can also occur. ...
... Incubation of Yeast Cells with Grape-Derived Volatile Compounds (Experiment 1). The conditions described by Ugliano et al. 10 were used for this experiment. Yeasts were cultivated in YPD medium and incubated at 30°C, under shaking (150 rpm). ...
Terpenes are important contributors wine aroma. Free and glycosidically bound terpenes are primarily formed in grapes. During fermentation they undergo to important transformation catalysed by yeast, so that the terpenes profile of grape is substantially different from that of the corresponding wine. The present paper assessed the ability of a Saccharomyces cerevisiae strain to biotransform 17 different terpenes. Biotransformation was performed by placing target compounds in incubation with resting cells. Volatile compounds produced were extracted by solid phase extraction (SPE) and analysed by GC-MS. Geranyl acetate, neryl acetate, citronellyl acetate and menthyl acetate were formed from the corresponding terpene alcohols. β-Citronellol was the main product of geraniol biotransformation; geranial, an intermediate of this pathway, has also been detected. Limonene was hydroxylated by yeast to form carveol, trans-2,8-menthadien-1-ol and cis-2,8-menthadien-1-ol. Moreover, yeast cells were found to be able to adsorb a significant portion of the terpenes present in the reaction batches, the extent of this phenomenon being linked to terpenes hydrophobicity.
... The conversion of these compounds to free monoterpenoids can be carried out via acidic or enzymatic hydrolysis by enzymes (especially βglucosidases) from grapes and/or microorganisms (non-Saccharomyces yeasts, Saccharomyces yeasts, and lactic acid bacteria (LAB)) during the alcoholic and malolactic fermentation processes (Fig. 1). The rates of acid hydrolysis in must have been observed as being too low for most of the released monoterpenoids (Ugliano et al. 2006;Williams et al. 1982). ...
... Indeed, it could be shown that the concentrations of glycosides decreased between 22% and 28% during fermentation, while the decrease in nonfermented samples was only approximately 5% over the same duration (Ugliano et al. 2006). ...
... Therefore, grape β-glucosidase is regarded as having a low contribution to the release of monoterpenoids from aglycones. In particular, numerous extracellular hydrolytic enzymes, such as β-glucosidase, α-arabinosidase, α-rhamnosidase, αxylosidase, and α-apiosidase, have been detected in both S. cerevisiae and non-Saccharomyces species (Charoenchai et al. 1997;Darriet et al. 1988;Ugliano et al. 2006). In addition, it has been proposed that the hydrolysis of monoterpenoids could also be conducted by exo-βglucanase enzymes of yeasts (Gil et al. 2005). ...
Although there are many chemical compounds present in wines, only a few of these compounds contribute to the sensory perception of wine flavor. This review focuses on the knowledge regarding varietal aroma compounds, which are among the compounds that are the greatest contributors to the overall aroma. These aroma compounds are found in grapes in the form of nonodorant precursors that, due to the metabolic activity of yeasts during fermentation, are transformed to aromas that are of great relevance in the sensory perception of wines. Due to the multiple interactions of varietal aromas with other types of aromas and other nonodorant components of the complex wine matrix, knowledge regarding the varietal aroma composition alone cannot adequately explain the contribution of these compounds to the overall wine flavor. These interactions and the associated effects on aroma volatility are currently being investigated. This review also provides an overview of recent developments in analytical techniques for varietal aroma identification, including methods used to identify the precursor compounds of varietal aromas, which are the greatest contributors to the overall aroma after the aforementioned yeast-mediated odor release.
... 1 Volatile compounds, such as terpenes, C13-norisoprenoids and benzene compounds, are linked to sugar molecules forming glycosides, which can be subsequently hydrolyzed by glycosidase enzymes from grapes or yeasts. 2 The varietal aroma of a wine is, therefore, conditioned by the grape variety, climatic conditions and agronomic practices, but oenological practices such as skin maceration, the type of yeast or the addition of exogenous enzymes can increase the concentration of varietal compounds in the wine. 3,4 In aromatic grape varieties, a few compounds have a great impact on the wine aroma, related to the characteristic aroma of the variety. In other cases, the aroma of the wine is the result of a synergy between several volatile constituents, among which the compounds formed during fermentation (aldehydes, esters, lactones) can play an important role. ...
... Terpenes can undergo different modifications during fermentation, either due to the release of their precursors by yeasts or by the effect of chemical reactions. 4,5 Hydroxylinalool once again stands out as the main terpene, both in free and bound form, followed by linalool and ⊍-terpineol. These compounds have been highlighted as being responsible for the typical aroma of stone fruits (peach, apricot) in Viognier wines. ...
BACKGROUND
High‐power ultrasound is a novel and non‐thermal technique normally used in red vinification to increase the extraction of phenolic compounds. However, few studies have been carried out on its effect on the extraction of aroma compounds and their precursors in white grapes. This study evaluates the effect of high‐power ultrasound at winery scale in the maceration of Viognier grapes on the content of varietal volatile compounds (free and glycosidically bound) in musts and wines, in comparison with wines from direct pressing and from short skin maceration.
RESULTS
The pre‐fermentative ultrasound treatment of the grapes produced an increase in most of the varietal compounds of musts and wines, both in the free fraction and in the bound one, especially in the C6 alcohols, terpenes and norisoprenoids, some of them of sensory relevance, while the effect on esters and lactones was less evident. Ultrasound maceration allowed us to obtain wines of higher aromatic intensity, with a more pronounced varietal character.
CONCLUSION
The pre‐fermentative ultrasound treatment of Viognier grapes increases the aromatic potential of the wines, as it favors the extraction of free and bound varietal volatile compounds. In addition, it allows the maceration time of the grapes to be reduced compared to conventional pre‐fermentation techniques, thus avoiding oxidative processes that could negatively affect the aroma of the wines. © 2022 Society of Chemical Industry.
... In Corvina the influence of withering on these pathways is complex, with upper steps of the pathway being downregulated but late biosynthetic steps upregulated [16]. In addition to free forms of terpenes, grapes also contain non-volatile glycosylated forms of these compounds, which in Corvina can contribute significantly to terpenes level in finished through enzymatic and chemical hydrolysis during vinification [35,37]. Although in the present study differences in glycosidically-bound terpenes in the finished wines were relatively small, we observed generally higher concentrations of bound terpenes in withered wines ( Table 2). ...
... Contrary to linalool, citronellol, the second most abundant monoterpene alcohols detected, increased with withering. In non-aromatic grapes such as Corvina, formation of citronellol is connected to the ability of yeast to reduce available geraniol including the portion derived from hydrolysis of geraniol glyosidic precursors [37,38]. Bound geraniol in finished wines increased in one of the withering modalities, supporting a possible contribution of bound geraniol to free citronellol levels. ...
Withering is a practice traditionally used in various regions to produce sweet or dry wines. During withering there is an increase in sugar content but also a modification in volatile compound profiles. Controlling metabolic changes through the dehydration process to obtain wines with desired characteristics is therefore a challenging opportunity. The effects of two different withering technologies, post-harvest or on-vine with blocked sap vessel flow, on the volatile profile of young and aged Corvina red wines was investigated. The results showed that modulation of wine aroma due to the withering process is associated with fermentative metabolites, such as esters, higher alcohols, and acids, as well as grape-related compounds such as C6 alcohols, terpenes and norisoprenoids. Significant differences were also found by comparing the two withering techniques. Post-harvest in a traditional “fruttaio” warehouse wines showed higher content of ethyl acetate, ethyl butanoate, β-citronellol and 3-oxo-α-ionol, whereas post-harvest withering on-vine increased β-damascenone in wines. The type of withering technique has an influence on the evolution of some aroma compounds during the aging of wine, among them linalool, (E)-1-(2,3,6-trimethylphenyl)buta-1,3-diene (TPB), n-hexyl acetate, ethyl acetate, ethyl 3-methylbutanoate, 3-oxo-α-ionol and β-damascenone.
... First of all, these are terpenes, in which only 10% of the must are in volatile form. The majority of these compounds are linked to saccharides by glycosidic bonds [60][61][62]. The dominant amount of volatile compounds that shape the aroma of wines is formed during fermentation and maturation. ...
Wood chips contain numerous active compounds that can affect the wine’s characteristics. They are commonly used in red grape wines, whisky, cherry and brandy, but in fruit wines, production is not typically utilised. The aim of this study was to compare the impact of an oak barrel ageing with the effect of the addition of chips made from various types of wood (oak, maple, cherry, apple) and with various degrees of toasting to the apple wines on their antioxidant, oenological and sensory properties. The oenological parameters, the polyphenols content, antioxidant activity and content of volatile odour-active compounds were assessed. It was shown that ageing in the presence of wood chips had a less noticeable effect on the oenological and sensory parameters of the wine than barrel ageing. Moreover, wood chips used did not significantly affect the acidity, alcohol and extract content of apple wines. Wines aged in the presence of oak chips (particularly lightly toasted) exhibited the greatest increase in polyphenols, while the polyphenol content of wines aged in the presence of other chips was not dependent on their toasting degree. The ageing of fruit wines with wood chips influences the volatile profile and the olfactory sensations, which can improve their quality.
... It has been shown that yeasts belonging to the Saccharomyces cerevisiae species exhibit a significantly reduced potential to release volatile terpenoids, compared to wild yeasts such as Hanseniaspora uvarum, Debaryomyces hansenii, Metschnikowia pulcherrima, Kloeckera apiculata, Pichia anomala, Meyerozyma guillermondii, and Wickerhamomyces anomalus [48][49][50]. Among lactic acid bacteria, Oenococcus oeni, Lactiplantibacillus (formerly Lactobacillus) plantarum, and Levilactobacillus (formerly Lactobacillus) brevis have also been observed to release free volatile monoterpenoids [9,[51][52][53][54][55][56][57][58]. The aforementioned microorganisms exhibit this ability due to the presence of enzymes that hydrolyse glycosidic bonds, including β-D-glucosidase (which releases glucose from the volatile compound), α-L-arabinofuranosidase (catalyses the hydrolysis of interosidic bonds within the arabinofuranosyl glucoside precursor of volatile compounds), α-L-rhamnosidase (enables the sequential hydrolysis of the rhamnosyl glucoside precursors of volatile compounds), and α-apiosidase (cleaves the terminal sugar and apiose, releasing the corresponding β-D-glucoside) [5,47,[59][60][61][62]. ...
Volatilomics is a scientific field concerned with the evaluation of volatile compounds in the food matrix and methods for their identification. This review discusses the main groups of compounds that shape the aroma of wines, their origin, precursors, and selected metabolic pathways. The paper classifies fruit wines into several categories, including ciders and apple wines, cherry wines, plum wines, berry wines, citrus wines, and exotic wines. The following article discusses the characteristics of volatiles that shape the aroma of each group of wine and the concentrations at which they occur. It also discusses how the strain and species of yeast and lactic acid bacteria can influence the aroma of fruit wines. The article also covers techniques for evaluating the volatile compound profile of fruit wines, including modern analytical techniques.
... In isolation, higher alcohols and fatty acids are often perceived as having unpleasure odors and are not considered to contribute positively to wine aroma, except for 2-phenylethanol, which provides desirable rose and honey aromas (Ugliano, Bartowsky, McCarthy, Moio, & Henschke, 2006). The original wine sample after AF contained relatively high concentrations of total higher alcohols (282 mg/L). ...
Malolactic fermentation (MLF) is a crucial process to enhance wine quality, and the utilization of indigenous microorganisms has the potential to enhance wine characteristics distinct to a region. Here, the MLF performance of five indigenous Oenococcus oeni strains and six synthetic microbial communities (SynComs), were comparatively evaluated in Cabernet Sauvignon wine. In terms of malate metabolism rate and wine aroma diversity, the strain of O. oeni Oe114–46 demonstrated comparable MLF performance to the commercial strain of O. oeni Oe450 PreAc. Furthermore, the corresponding SynComs (Oe144–46/LpXJ25) exhibited improved fermentation properties, leading to increased viable cell counts of both species, more rapid and thorough MLF, and increased concentrations of important aroma compounds, such as linalool, 4-terpinenol, α-terpineol, diethyl succinate, and ethyl lactate. These findings highlight the remarkable MLF performance of indigenous O. oeni and O. oeni-L. plantarum microbial communities, emphasizing their immense potential in improving MLF efficiency and wine quality.
... The reaction can undergo a two-step hydrolysis through the action of an appropriate glycosidase (arabinofuranosidase, rhamnopyranosidase or apiofuranosidase) to release the terminal sugar (arabinose, rhamnose, or apiose, respectively) followed by β-glucosidase action to release the bound volatile compound. For monoglucosidic precursors, only the action of β-glucosidase is needed [5,7,8]. ...
Selective enhancement of wine aroma was achieved using a broad spectrum of exogenous glycosidases. Eight different enzyme preparations were added to Verdejo wine, resulting in an increase in the levels of varietal volatile compounds compared to the control wine after 15 days of treatment. The enzyme preparations studied were robust under winemaking conditions (sulfur dioxide, reducing sugars, and alcohol content), and no inhibition of β-glucosidase activity was observed. Significant differences were detected in four individual terpenes (α-terpineol, terpinen-4-ol, α-pinene, and citronellal) and benzyl alcohol in all the treated wines compared to the control wine, contributing to the final wine to varying degrees. In addition, a significant increase in the other aromatic compounds was observed, which showed different patterns depending on the enzyme preparation that was tested. The principal component analysis of the data revealed the possibility of modulating the different aromatic profiles of the final wines depending on the enzyme preparation used. Taking these results into account, enhancement of the floral, balsamic, and/or fruity notes of wines is possible by using a suitable commercial enzyme preparation.
... The production of monoterpenes from different precursors depends on S. cerevisiae strain, although its hydrolysis action on bonded terpene fraction in the first fermentation stages is one of the most relevant contributions [37]. Linalool, citronellol, and geraniol were the terpenes identified and quantified in the evaluated wines, which are associated with floral odors [38]. ...
This chapter synthetizes the main results that our research group has obtained about the specific influence of a commercial Saccharomyces cerevisiae strain on the aromatic profile of fermented musts from four minority grape varieties (Vitis vinifera L.) cultivated in Castilla-La Mancha (Spain), that is, Moribel, Tinto Fragoso, Albillo Dorado and Montonera del Casar. In addition, wines made from the grape cultivars Tempranillo and Airén were evaluated. To determine the main yeast-derived odor relevant in these grape varieties, the aromatic profiles of grape cultivars and the resulting wines were studied by gas chromatography coupled to mass spectrometry and wines were subjected to Napping, a rapid sensory evaluation method. The results revealed wine sensory differences which are consequence of different aromatic profiles of wines produced with these grape cultivars. The combination of quantitative chemical analysis of volatile compounds together with sensory analysis of wines point out different patterns of aroma compound formation and release. Thus, the yeast strain used in the fermentation step is one of the main factors that affect the sensory properties of wines.
... Yeasts and their influence on the chemical composition of wines have been demonstrated through studying fermentations which, being carried out with different S. cerevisiae strains and using the same must, show wide variability in the compounds produced [83][84][85]. ...
The aim of this study was to isolate and characterize autochthonous Saccharomyces cerevisiae yeasts from Cabernet Sauvignon grape must and to analyze how they impacted the final characteristics of the wines obtained from the same type of must. This work was carried out in a “Pago” winery located in Requena, Spain. Twenty-two isolates were obtained from grape must. After molecular identification and typing, 11 different strains were determined. Growth-related parameters and metabolic characteristics (glucose and fructose consumption and ethanol, glycerol and acetic acid production) were determined via laboratory-scale fermentations (50 mL) of Cabernet Sauvignon must. From 2 L fermentation batches, the residual sugar, density, ethanol concentration, titratable and volatile acidities, pH and polyphenolic and volatile compounds were determined, as well as the sensory attributes of the produced wines. Differences between strains in the growth and metabolic parameters were observed. Eleven S. cerevisiae strain profiles were characterized to establish which strain or strains of the selected yeasts would produce the highest polyphenolic and aromatic concentrations of the red Cabernet wines made in the “Pago winery”, to then multiply them for their use to make the red wines of this winery.
... The reaction is very specific since the linalool is seldom released, and this could be due to the steric hindrance of the tertiary alcohol itself [57]. However, some researchers [58] observed a release of linalool during wine fermentation performed with S. cerevisiae and S. bayanus. The hydrolysis of glycosidically bound tertiary alcohols, and then, depends on the strain and the fermentation conditions [13]. ...
The biodiversity of some Saccharomyces (S.) strains for fermentative activity and metabolic capacities is an important research area in brewing technology. Yeast metabolism can render simple beers very elaborate. In this review, we examine much research addressed to the study of how different yeast strains can influence aroma by chemically interacting with specific aromatic compounds (mainly terpenes) from the hop. These reactions are commonly referred to as biotransformations. Exploiting biotransformations to increase the product’s aroma and use less hop goes exactly in the direction of higher sustainability of the brewing process, as the hop generally represents the highest part of the raw materials cost, and its reduction allows to diminish its environmental impact.
... The terpenes produced can then be glycosylated in the berry. During fermentation, these bound forms are then cleaved by the yeasts releasing the aglycone [18]. Terpenes are an important contributor to floral and citric notes and are found in higher concentrations in aromatic varieties such as Muscat [19,20]. ...
In this work, the aromatic characterization of commercially available Prosecco wines with a price range between EUR 7 and 13 was carried out. These wines came from three different areas of origin: Valdobbiadene, Asolo and Treviso. Seventy volatile compounds were identified and quantified in the wines. Quantitatively, the wines were mainly characterized by compounds of fermentation origin (alcohols, acids, esters), and C6-alcohols, and to a lesser extent, terpenes, low molecular weight volatile sulfur compounds (VSC), and benzenoids. To determine their impact on the aroma of Prosecco wine, the respective OAVs were calculated. The molecules with higher OAV were ethyl hexanoate, isoamyl acetate, and β-damascenone. More generally, esters, responsible for fruity notes, seemed to play a major role in the aroma of Prosecco wine. Investigation into the possible effect of different production zones indicated 16 significantly different compounds accounting for differences between the various areas of origin of the wines, being mostly VSC, esters and C6-alcohols. A sensory evaluation through a sorting task highlighted the formation of clusters; wine samples were divided into two main groups partially attributable to the areas of origin. From a chemical point of view, cluster A was richer in esters, while cluster B had, on average, higher concentrations of compounds associated with wine aging such as cyclic terpenes, norisoprenoids (TDN and vitispirane), and VSC.
... In this sense, the genes reported that encode glucosidase activity are BGL2, EXG1, SPR1, and ORF YIR007W. 11,12,17 Nitrogen content can serve as a means of modulating the production of yeast-derived aroma in alcoholic fermentation for a given strain to some degree. Although the fermentation environment significantly influences secondary metabolism, the response to the environment depends on the yeast strain selected for fermentation. ...
The concentration of nitrogen in must is critical to yeast fermentation efficiency and wine aroma profile. The present work determined the effect of the amount of yeast assimilable nitrogen (YAN) on fermentation kinetics, aroma production, and gene expression patterns of the wine yeast Saccharomyces cerevisiae. Fermentations were performed under two different YAN concentrations of must. Acetate esters, linalool, and nerol appeared to be clearly affected by the different YAN levels. Real-time-PCR results revealed that the genes involved in ethyl and acetate esters production recorded, in general, higher transcript levels under high nitrogen supplementation. In addition, an up-regulation of the BGL2 and EXG1 genes, which are related to terpenes production, was observed in the case of high nitrogen content and it is well corresponded to the terpenol concentration found. Our study revealed the impact of nitrogen supplementation on yeast metabolism and its importance to adjust wine's aromatic composition and sensory profile.
... Supplementary Figure 1 showed the related content of the generation pathway of β-damascenone (Sun T. H. et al., 2022). In addition, β-damascenone can also be produced by some non-Saccharomyces yeasts during the fermentation processes of wine and beer, such as Cyberlindnera saturnus, Debaryomyces hansenii, Hanseniaspora uvarum, Metschnikowia pulcherrima, and Wickerhamomyces anomalus (Ugliano et al., 2006;Swangkeaw et al., 2010;Lloyd et al., 2011;Methner et al., 2022). However, to date, β-damascenone in Baijiu has rarely been reported. ...
As a C13-norisoprenoid aroma substance, β-damascenone is a highly important aromatic compound and an active constituent. The purpose of this study was to investigate the change law of β-damascenone during the light-flavor Baijiu brewing process, and screen the indigenous microbial strains that produce this compound and optimize fermentation parameters for improving β-damascenone production using a statistical approach. In this project, Wickerhamomyces anomalus YWB-1 exhibited the highest producing activity of β-damascenone. Fermentation conditions were optimized for β-damascenone production using a one-factor-at-a-time (OFAT) approach. A Plackett-Burman design was subsequently adopted to assess the effects of initial pH, incubation temperature, inoculum size, fermentation period, and original Brix degree. Analysis of variance (ANOVA) showed that the correlation coefficient (R2) of the executive model was 0.9795, and this value was significant (p < 0.05). Three significant variables were optimized at three different coded levels using a Box-Behnken design (BBD) of response surface methodology (RSM). Here, 7.25 μg/L β-damascenone was obtained under the following optimum conditions: initial pH of 3.31, original Brix degree of 10.53%, and fermentation period of 52.13 h. The yield was increased 3.02-fold compared with that obtained under unoptimized conditions. This information is conducive to the control of flavor production by regulating variable parameters in Baijiu fermentation.
... Different strains of S. cerevisiae can produce significantly different flavour profiles when fermenting the same must. This is a consequence of the ability of wine yeast stains to both release varietal volatile compounds from grape precursors and synthesise de novo yeast-derived volatile compounds [77,[128][129][130]. Molina et al. (2009) showed that musts fermented by two strains differed in sensory perception and descriptive analysis [131]. ...
A wine’s aroma profile is an important part of the criteria affecting wine acceptability by consumers. Its characterisation is complex because volatile molecules usually belong to different classes such as alcohols, esters, aldehydes, acids, terpenes, phenols and lactones with a wide range of polarity, concentrations and undesirable off-aromas. This review focused on mechanisms and conditions of the formation of individual aroma compounds in wine such as esters and higher alcohols by yeast during fermentation. Additionally, aroma losses during fermentation are currently the subject of many studies because they can lead to a reduction in wine quality. Principles of aroma losses, their prevention and recovery techniques are described in this review.
... A wide range of yeasts could be potentially used for their glycosidase activity. Whilst previous research has shown that all yeasts have some glycosidic hydrolyzing activity, their activity might be different, according to the different chemical structure of the sugar and the aglycon moieties [30]. A study on Fiano wine specifically investigated the release of free and bound volatile compounds as affected by the enzymatic or acid hydrolysis. ...
The type of yeast strain used for wine alcoholic fermentation dramatically affects its final volatile composition and, therefore, its sensory properties. In this study, the influence of four oenological Saccharomyces strains (three S. cerevisiae and one S. bayanus) on wine volatile composition was determined on the Fiano variety, a typical cultivar from the Campania region (Italy), fermented in oak barrique. Fiano wines were analyzed by means of gas chromatography/mass spectrometry (GC/MS) and gas chromatography/olfactometry (GC/O). The results showed that the four selected yeast strains had a significant impact on the majority of volatile compounds as shown by the concentration of volatile compounds and based on the Aroma Extract Dilution Analysis (AEDA) values for many of the odor volatile compounds. This resulted in a dramatic change of the odor impact of the wines, such as the “fruity” attribute, which was higher compared to the control, and caused some changes of other odor attributes, particularly “floral”, “phenolic” and “honey”. This research demonstrates the potential of using these selected yeast strains and this technological approach of oak fermentation for this typical white wine grape variety.
... The glycosidically bound fraction of terpenes and norisoprenoids present in the wines was very small compared to the free fraction, which assumes that during the fermentation process, an important release of its precursors has occurred thanks to the glycosidic activity of yeasts [34,35]. MW treatment showed only a slight increase of this fraction in samples. ...
This study evaluates the effect of microwave treatment in grape maceration at laboratory scale on the content of free and glycosidically bound varietal compounds of must and wines and on the overall aroma of wines produced with and without SO2. The volatile compounds were extracted by solid phase extraction and analyzed by gas chromatography–mass spectrometry, carrying out a sensory evaluation of wines by quantitative descriptive analysis. Microwave treatment significantly increased the free and bound fraction of most varietal compounds in the must. Wines from microwave maceration showed faster fermentation kinetics and shorter lag phase, resulting in an increase in some volatile compounds of sensory relevance. The absence of SO2 caused a decrease in concentration of some volatile compounds, mainly fatty acids and esters. The sensory assessment of wines from microwave treatment was higher than the control wine, especially in wines without SO2, which had higher scores in the “red berry” and “floral” odor attributes and a more intense aroma. This indicates that the pre-fermentative treatment of grapes with microwaves could be used to increase the wine aroma and to reduce the occurrence of SO2.
... Numerous studies have shown that β-glycosidase is present in yeast species in grapes and wine, and that β-glucosidase is found in S. cerevisiae (Henschke, 2006;Hernández et al., 2003;Gil, 2005) and non-Saccharomyces yeasts (Fia et al., 2010;Hu et al., 2016). The presence of β-glucosidase is quite rare in S. cerevisiae (Spagna et al., 2002;Sun et al., 2014), and most studies have found higher enzyme activity in non-Saccharomyces species (Mateo et al., 2011;Otero et al., 2003;Strauss et al., 2001;Styger et al., 2011;Swangkeaw et al., 2009). ...
β‐glucosidase is a pivotal enzyme that hydrolyzes bound volatile aromatic compounds. However, the activity of β‐glucosidase in winemaking and the mechanism by which it affects the flavor and taste of wines have not been fully investigated. In this study, we profiled the characteristics of β‐glucosidase derived from wine‐related yeasts isolated from different wine‐making regions in China, and analyzed the enzyme activity from different parts of the cells under aerobic and anaerobic conditions. A total of 56 strains of wine‐related yeasts producing β‐glucosidases were screened using the YNB‐C medium (YNB 6.7 g L–1, cellobiose 5 g L–1, pH 5.0). We found that strain Clavispora lusitaniae C117 produced the highest enzyme activity (152.39 µmol pNP ml–1 h–1). In most strains, β‐glucosidase were located in whole cells (periplasmic space) and permeabilized cells (intracellular). The non‐Saccharomyces species had the highest enzymatic activity in a strain‐dependent manner. Under aerobic conditions, C. lusitaniae C117, Hanseniaspora guilliermondii A27‐3‐4, Metschnikowia pulcherrima F‐1‐6, and Pichia anomala C84 had the highest β‐glucosidase activity. We further investigated the β‐glucosidase activity during the wine fermentation and the effects of sugar, pH, temperature, and ethanol on the enzyme activities of P. anomala C84 and commercial Saccharomyces yeast strains RC212 and VL1. The presence of fructose, glucose, and sucrose strongly inhibited enzyme activity. Similarly, low pH and low temperature inhibited the activity of β‐glucosidase, whereas ethanol promoted enzyme activity. Our findings provide a theoretical basis on understanding the different yeast characteristics of β‐glucosidase and their potential application for further improving wine aroma complexity.
... The SPME extract was injected into the port of an Agilent 7890A-5975C GC/MSD instrument equipped with a DB-5 capillary column (30 m × 0.25 mm, 0.25 µm film thickness) (Agilent Technologies, Santa Clara, CA, USA) and desorbed at 250 • C for 3 min (Ugliano et al., 2006). The injection port was operated in split mode (1:10), and 99.999% pure helium was used for vial pressurization and as the carrier gas. ...
The synergistic effects of ultrasound and β‐d‐glucosidase in aroma of orange juice were investigated. β‐d‐Glucosidase significantly increased the content of ester, aldehyde, alcohol, terpene, acid, and phenol, and insignificantly increased the ketone content in orange juice. Enzyme‐treated orange juice, compared with fresh untreated orange juice, was found to contain 15 novel aroma compounds, whereas three aroma compounds disappeared. Ultrasound improved the enzymatic action and the retention of more active flavors in juice than treatment with enzyme alone. However, simultaneous ultrasound and enzyme treatment decreased aroma quality. Therefore, the choice of the mode of ultrasound treatment is highly important. The present investigation will provide a reference for aroma‐enhancing application of ultrasound combined with β‐D‐glucosidase.
Practical Application
The study supplies a reference method for the aromatization of fruit juice.
... Monoterpenes can be found in grapes and musts as free aroma compounds but, depending on the grape variety, they can be present in much higher concentration (90% in Muscat varieties), being linked to sugar moieties, the so-called terpene glycosidic non-volatile precursors (Gunata, Bayonove, Baumes, & Cordonnier, 1985). Conversion of these compounds into terpenes is mainly carried out through enzymatic hydrolysis, for example by β-glucosidases (from grapes or micro-organisms) during alcoholic and malolactic fermentation processes and, to a lesser extent, by acidic hydrolysis in musts (Charoenchai, Fleet, Henschke, & Todd, 1997; Günata, Bayonove, Tapiero, & Cordonnier, 1990;Ugliano, Bartowsky, McCarthy, Moio, & Henschke, 2006). During wine storage and under acidic, oxidative or high temperature conditions, monoterpenes can be transformed into different compounds that may be more or less aromaintensive and may disrupt the original character of the wine (Marais, 2017;Ruiz et al., 2019). ...
... A number of different factors determine wine terpene content. Terpenes are produced in grapes through both the 1-deoxy-d-xylulose-5phosphate/methylerythritol phosphate (DOXP/MEP) pathway and the mevalonic acid (MVA) pathway [35], and in the case of non-aromatic grapes such as Trebbiano they are found mostly in glycosidically bound form, which are then released by yeast during fermentation [36]. The different concentrations of terpenes could be due to viticultural and environmental factors [37][38][39], so that they can be also good markers of geographical wine origin [11]. ...
Lugana and Verdicchio are two Italian white wines with a Protected Designation of Origin (PDO) label. These two wine types are produced in different regions using the same grape variety. The aim of this work is to investigate the existence of volatile chemical markers that could help to elucidate differences between Lugana and Verdicchio wines both at chemical and sensory levels. Thirteen commercial wine samples were analyzed by Gas Chromatography-Mass Spectrometry (GC-MS), and 76 volatile compounds were identified and quantified. Verdicchio and Lugana had been differentiated on the basis of 19 free and glycosidically bound compounds belonging to the chemical classes of terpenes, benzenoids, higher alcohols, C6 alcohols and norisoprenoids. Samples were assessed by means of a sorting task sensory analysis, resulting in two clusters formed. These results suggested the existence of 2 product types with specific sensory spaces that can be related, to a good extend, to Verdicchio and Lugana wines. Cluster 1 was composed of six wines, 4 of which were Lugana, while Cluster 2 was formed of 7 wines, 5 of which were Verdicchio. The first cluster was described as “fruity”, and “fresh/minty”, while the second as “fermentative” and “spicy”. An attempt was made to relate analytical and sensory data, the results showed that damascenone and the sum of 3 of esters the ethyl hexanoate, ethyl octanoate and isoamyl acetate, was characterizing Cluster 1. These results highlighted the primary importance of geographical origin to the volatile composition and perceived aroma of Lugana and Verdicchio wines.
... Terpenes and their derivatives have a great sensory impact in wines from aromatic varieties such as Muscat, due to their low odor thresholds and pleasant aromas (floral or fruity), but they are less relevant in the aroma of wines from other grape varieties, especially in the case of red wines [38]. Although they come from the grape, many of them undergo modifications during fermentation, mainly by the liberation of its precursors due to the possible glycosidic activity of yeasts [4,39]. Hydration or oxidation reactions can also affect terpenes, giving rise to compounds with lower aromatic potential. ...
This study presents the effect of the application of high-power ultrasound to crushed grapes, at a winery-scale, on the content of varietal volatile compounds (free and glycosidically-bound) in musts and on the overall aroma of wines. Two different frequencies (20 kHz and 28 kHz) were tested and the combination of grape sonication and different maceration times on wine aroma was also evaluated. The volatile compounds were isolated by solid phase extraction and analyzed by gas chromatography-mass spectrometry, carrying out a sensory evaluation of wines by quantitative descriptive analysis. Sonication produced an increase in the concentration of free varietal compounds such as C6 alcohols, terpenes and norisoprenoids in musts and also in wines made by 48 h of skin maceration, being less efficient in the extraction of the bound fraction. Fermentation compounds were also positively affected by ultrasound treatment, although this effect was variable depending on the frequency used, the maceration time and the type of compound. All the wines made from sonicated grapes had better scores in the evaluated olfactory attributes with respect to the control wines. Our results indicate that sonication could produce an increase in the content of some volatile compounds of sensory relevance, obtaining wines with an aroma quality similar or higher than those elaborated with longer maceration times.
... The first technique leads to the greater extraction of aromatic compounds and precursors from the skins by means of maceration in the must before the fermentation [19]. The use of yeasts and enzymes with glycosidase activity favour the release of the aromatic compounds that are found in the grape combined with sugars in non-aromatic form [20,21]. ...
The aim of this study was to evaluate the influence of vinification techniques on volatile compounds and sensory profiles in young Palomino fino white wines. Four winemaking techniques (pellicular maceration, supra-extraction and use of commercial yeast strains and of β-glycosidase enzymes) were implemented to enhance the aromatic quality of wines elaborated from this neutral variety of grape. Volatile compound content, aromatic profile (OAVs) and sensorial analysis were determined. The results showed that all the vinification techniques studied led to an increase in volatile compounds compared to the control wine. Likewise, an influence of the vineyard and must extraction method on these compounds was observed. However, the greatest changes in aroma activity and sensory profile were a result of the pellicular maceration and supra-extraction techniques. The latter was differentiated by the highest content of terpenes and, consequently, the highest odour activity values of floral series. In addition, the supra-extraction was a very selective technique since it extracted terpenes and aromatic precursors, but not the acids responsible for the fatty characteristic, such as octanoic acid. In terms of sensory profile, the supra-extraction technique improved the intensity of the Palomino fino white wine and its aromatic quality with a previously not-determined floral character.
... Among these, geraniol, 3-hydroxy-β-damascone, and vanillin were for the most part affected by yeast and not by area. S. cerevisiae is able to synthesize terpenes such as geraniol, but the contribution of this pathway is expected to be minor compared to release from glycosidic precursors and/or bio transformation of other terpenes (Ugliano, Bartowsky, McCarthy, Moio, & Henschke, 2006). A compound typically associated with use of oak but observed in the present study was ethyl vanillate, which was the most abundant benzenoid found in Corvina and Corvinone. ...
Volatile composition and sensory properties of Corvina and Corvinone red wines in relationship to grape origin, yeast strain and inoculated vs. spontaneous fermentation were investigated. Experimental wines were produced using freshly harvested grapes of the two varieties coming from two different areas. The results indicated that, by affecting grape composition, grape origin had a primary impact on wine aroma chemical and sensory properties. From a chemical point of view, this effect was associated not only with grape-derived compounds but also to some extent with fermentation-derived esters. Yeast strains influence was mostly associated with higher alcohols and certain esters, whereas the main characteristic of spontaneous fermentation was increased concentration of ethyl acetate. Sensory analysis confirmed the greater impact of grape origin compared to yeast strain, indicating clusters of odor similarities which were mostly associated with variations in the content of ethyl esters, C6 alcohols, and norisoprenoids in Corvina and of norisoprenoids, cyclic terpenes, acetate esters, and ethyl acetate in Corvinone, respectively.
... Différentes levures peuvent être présentes au cours de la première étape de la fermentation, laissant ensuite la place à un autre type de levure, appelé maintenant S. cerevisiae Thèse de doctorat Marina Al Daccache (Barnett, 2000). Cette levure est largement utilisée pendant la fermentation due à son comportement contrôlé et répétitif ainsi que pour la libération de ses précurseurs d'arôme (Pretorius, van der Westhuizen et Augustyn, 1999;Ubeda et Briones, 2000;Dubourdieu et al., 2006;Ugliano et al., 2006). Cependant, la fermentation ne dépend pas d'un seul type de levure. ...
Ce travail de thèse concerne la valorisation des pommes libanaises en évaluant leur potentiel fermentaire en vue de l’élaboration du cidre, spécifiquement l’étape de la fermentation de ce processus. Pour cette fin, l’analyse de la composition chimique des pommes libanaises « Ace spur » a été effectué en comparaison avec une pomme à cidre « Kermerrien » utilisée industriellement en France pour la production du cidre. La variété de pomme libanaise « Ace spur » semble être convenable pour l’élaboration de cidre. De plus, une souche responsable de la fermentation spontanée de cette variété de pommes a été isolée et identifiée. Son potentiel fermentaire dans ces deux variétés de pommes a été par la suite étudié. La levure Hanseniaspora sp. isolée permet la fermentation des jus de pommes jusqu’à 4% (v,v) d’éthanol. Cette étude fournira pour la première fois des données sur la composition chimique de la pomme libanaise, sur une souche présente lors de sa fermentation, ainsi que sur son potentiel fermentaire. Également, les travaux de la thèse consistent à évaluer l’impact des procédés émergents : champs électriques pulsés et ultrasons sur la fermentation. Ces travaux visent à démontrer le potentiel d’implémentation de ces procédés industriellement. Nous proposerons une approche de traitement du jus de pommes en continu qui pourra être transposée de l’échelle laboratoire à l’échelle industrielle. L’application des technologies émergentes (champs électriques pulsés et ultrasons) induit une accélération des cinétiques fermentaires et une réduction du taux d’éthanol.
... This type of yeast is nowadays known as belonging to the Saccharomyces strains [77]. S. cerevisiae is largely used to produce alcoholic beverages due to its controlled and repetitive behavior as well as for the release of its aroma precursors [78][79][80][81]. Nevertheless, fermentation is the collaboration of different species of yeast and bacteria initially present in the product or found on the surface of the presses and fermenters. ...
Fermented apple beverages are produced all over the world with diverse characteristics associated with each country. Despite the diversifications, cider producers are confronted with similar issues and risks. The nature of the raw material, also known as the fermentation medium, plays a key role in fermentation. A well-defined composition of apples is, therefore, required to produce cider with good quality. In addition, ferment and its metabolism are important factors in the fermentation process. The producers of cider and other alcoholic beverages are looking in general for novel yeast strains or for the use of native strains to produce "authentic" and diversified beverages that are distinct from each other, and that attract more and more consumers. Research articles on cider production are infrequent compared to wine production, especially on the impact of the chemical composition and microbial diversity of apples on fermentation. Even though the processing of fermented beverages is close in terms of microbial interactions and production, the study of the specific properties of apples and the production challenges of cider production is advantageous and meaningful for cider producers. This review summarizes the current knowledge on apple composition and the impact of the must composition on fermentation and yeast growth. In addition, the microbial diversity of cider, activities, and its influence on fermentation are reviewed.
... Pourtant, la contribution de S. cerevisiae dans la libération d'arômes à partir de précurseurs glycosidiques pendant la FA a été prouvée (Ugliano et al. 2006b ;Loscos et al. 2007 ;Hernández-Orte et al. 2008). Des enzymes autres que le β-glucosidase interviendraient donc dans la libération d'arôme. ...
La présence d’un métabolisme actif des bactéries lactiques dans le vin logé en fûts de chêne induit une augmentation de la concentration des composés volatils du bois. Ce phénomène a récemment été attribué à l'activité glycosidique des bactéries. Le glucoside précurseur d'un composé majeur de l’arôme boisé (whiskylactone) a déjà été identifié et quantifié dans le bois de chêne. Mais aucune donnée n'était disponible jusqu’à présent concernant l’identification formelle des précurseurs pour d’autres arômes du bois de chêne.Un premier travail a permis de montrer que les précurseurs monoglycosides n'existaient pas dans le bois de chêne, dans les spiritueux et dans le vin. L'étude a été réalisée à l’aide de la technique UPLC-FT/MS, en utilisant la vanilline-β-D-glucopyranoside, la vanilline-β-D-xylopyranoside, et la coniféraldéhyde-β-D-glucopyranoside, synthétisées par réaction par transfert de phase. Dans un deuxième temps, une purification des précurseurs glycosidiques complexes a été réalisée à l’aide de la Chromatographie de Partage Centrifuge (CPC) à partir d’un extrait de bois de chêne. Le choix du système de solvants a été basé sur une égale répartition dans les deux phases de la libération d’arômes par hydrolyse enzymatique. Cela a conduit à la détermination du nouveau concept de coefficient de partage d’activité Kca. Après purification et fractionnement, la vanilline galloylglucoside, le triméthoxyphénol-galloyl-glucoside et le macarangioside E ont été isolés du bois et identifiés par HPLC-ESI-MS et RMN. Ces précurseurs ont été quantifiés dans différentes espèces de chêne par HPLC-QqQ-MS. Ces trois composés sont les précurseurs respectivement de la vanilline, du 3,4,5-triméthoxyphénol et du 3-oxo-α-ionol. Par dégradation thermique, le macarangioside E peut conduire à la mégastigmatriénone et à la 4-oxo-isophorone, dont les notes aromatiques sont le tabac et l’encens. Ces composés complètent la connaissance que nous avons de l’arôme boisé du vin et contribuent ainsi à une meilleure compréhension de la genèse du bouquet tertiaire.
... Besides the locality, VOC profiles of varietal wines are strongly affected by the strain of yeast used for fermentation. Each yeast strain produces significantly different concentrations of VOC which form an aromatic character of wine (Zott et al. 2011;Furdíková et al. 2014;Ugliano et al. 2016). ...
Grape juice of Cabernet Sauvignon was fermented with three axenic cultures of Saccharomyces cerevisiae (CS-V1, CS-V2, CS-V3) to determine the effect of yeast strain on the aroma of rosé wine. An analytical methodology based on headspace solid phase microextraction combined with comprehensive two-dimensional gas chromatography and high-resolution time-of-flight mass spectrometry was used for identification of volatile organic compounds (VOC) in resulting wines. This method allowed the identification of 97 VOC responsible for wine aroma which was strictly affected by the strain used for fermentation. Results of the statistical analysis showed that strains CS-V2 and CS-V3 had the highest similarity of VOC profiles while CS-V1 was significantly different. Wine fermented with yeast strain CS-V1 was characterized by a high concentration of hexyl octanoate, 2-phenylethyl octanoate and free terpenoids (farnesol, farnesyl acetate). Strain CS-V2 contributed to an increased relative concentration of 1-hexadecanol, 1-heptanol, 9-decenoic acid and nerolidol. Wine fermented with CS-V3 had a high level of benzaldehyde, hexyl hexanoate, benzeneacetaldehyde and terpenoids α-terpineol and nerol.
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... Reactions like alcoholic and malolactic fermentations, and chemical and enzymatic processes, produce a very complex aroma profile. Many authors have studied the influence of grape aroma on wine quality (among others: Gunata et al. 1985;Wilson et al. 1986;Voirin, et al. 1992a;Voirin et al. 1992b;Ugliano et al. 2006;Ugliano and Moio, 2008 ...
Aroma compounds are secondary metabolites that play a key role in grape quality. Terpenes, C13-norisoprenoids, phenols and non-terpenic alcohols are the most important aroma compounds in grapes and can be accumulated as free volatile or glycoconjugated molecules. The non-volatile glycosylated aroma precursors (GAP) group is the largest one, and it is present in all varieties of Vitis vinifera (L.), the most widely-used species for wine production. Agronomic practices such as irrigation, training systems, leaf removal and bunch thinning can impact the plant and fruit development. The modification of the source/sink relationship (S/S) with the scope of increasing the grape quality, is very common between viticulturists. These practices include bunch thinning, pruning, and the election of the number of buds/plant. Bunch thinning, a very extended practice in viticulture and which directly impacts on S/S, is one of the less researched practice regarding GAP. In many cases, DOC and IGT production protocols include a limit in the fruit yield per hectare. Then, viticulturists regulate yield by managing number of buds/hectare and/or by fruit thinning.The main objective of our work was to analyze the impact of the modifications of S/S balance on the biosynthesis of GAP. GAP are chosen in this research because: 1) they are present in every cultivar of Vitis vinifera, 2) they represent the biggest source of potential aromatic molecules, and 3) because these molecules incorporate glycosyl groups, their accumulation depends on the supply of carbohydrates and potentially on the carbon balance of the plant. The main objective of our work concerned the study of the impact of the S/S ratio on the biosynthesis of GAP, and its possible modulation depending on the genotype. Five questions were addressed: 1) Influence of the genotype on in the biosynthesis of GAP and its accumulation. The objective is to analyze the variability of GPA concentration at a given maturity stage among genotypes, including a set of varieties of V. vinifera (Marselan, Grenache, Muscat, Cabernet Sauvignon, Syrah and Chardonnay) and hybrids. V. vinifera x Muscadinia rotundifolia (G5). 2) Influence of the year on S/S balance and GAP concentration. 3) The impact of the S/S balance on the biosynthesis of GAP expressed in concentration (µg/L) and in quantity (µg/berry) as a function of grape development. 4) The relationship between primary and secondary metabolism (GAP and anthocyanins) and their modulation as a function of S/S balance. 5) Influence of the thinning date on the dynamics of GAP biosynthesis.The results showed that levels of glycosylated aromatic compounds varied according to genotype. Varieties whose grapes contain terpenic compounds (Muscat à petits grains blancs and the V. vinifera x Muscadinia rotundifolia G5 hybrid) showed the highest levels of GAP in both concentration and amount per fruit. These genotypes showed the highest values of GAP/sugar ratio. In general, genotypes producing non-colored berries had higher GAP/sugar ratios than colored berries. Despite strong inter-annual variation, the impact of the S/S ratio on GAP biosynthesis was found to be genotype-dependent.Thus, the GAP concentration was not affected during the modification of S/S in Cabernet-Sauvignon, while Muscat and Syrah showed large variations in GAP/berry contents as a function of the S/S ratio. The thinning date was also an important modulating factor in the increase of GAP, but varies according to genotype. In general, a significant decrease in the amount of primary metabolites accumulated in grapes is required to significantly increase the biosynthesis of secondary metabolites. This gain is very notable for anthocyanins, which are the most abundant carbon compounds after the primary metabolites (sugars and organic acids) in grapes. With regard to aromatic precursors, the impact is more moderate regardless of the family of glycosylated compounds.
... Table 4 shows the results from the ANOVA, according to which, the floral and citric notes have the greatest power of discrimination (lowest p-values) between the wines produced. These are attributed the highest score in the ranking test for wine E4 (fermented with S. bayanus at low temperature), which was characterized by high scores in Muscat typical citric and floral notes (in agreement with the observations of other authors regarding this yeast [40]), while the wine with the lowest score (E2, with added nitrogen) was characterized by very low intensities in these positive notes, as well as a clear olfactory defect of a chemical nature. Likewise, the fruity and floral notes of wines E3 and E5 (both subjected to pellicular maceration with pectolytic enzymes), were high. ...
In this study, a climate chamber, as an alternative method, has been used to dry raisins and the sensory profiles of the sweet sherry wines obtained have been evaluated. Other important factors, namely grape variety, vintage, vinification conditions, as well as the ageing method and its length of time, have also been considered. When heavy rainfall had been registered, the musts extracted from grapes dried under controlled conditions in a climate chamber showed a lower intensity of the musty off-odor compared to those elaborated with sun-dried grapes. The wine fermented at low temperature with Saccharomyces bayanus scored the highest in citric and floral notes, and this was preferred over all the other wines that were evaluated. The wines aged in oak barrels were preferred to both, wines aged in the presence of oak chips as well as those aged without any wood contact. The use of climate chambers to dry the grapes that are going to be used for the elaboration of sweet wines appears to be an advantageous alternative to the traditional method, since it allows a more precise control of the process and highly valued sweet wines from a sensory point of view are obtained thereby.
... As already reported by other studies [36][37][38], these results confirmed that from fermentation of the same grape must, different strains of S. cerevisiae can produce significantly different amounts of aromatic compounds, as a consequence of both the differential ability of wine yeast strains to release varietal volatile compounds from grape precursors and to synthesize de novo volatile compounds. Table 2.Oenological characteristics (average and standard deviation of three independent experiments) of 16 different S. cerevisiae strains. ...
Wine production by inoculated fermentation with commercial Saccharomyces cerevisiae strains is an ordinary practice in modern winemaking in order to assure the final quality of wine, although this procedure results in the production of highly homogeneous wines. The use of indigenous selected starters represents a useful tool to control alcoholic grape must fermentation, safeguarding the typical sensory characteristics of wine produced from specific regions. In this study, we selected three indigenous S. cerevisiae strains among 16 indigenous strains previously isolated from the spontaneous fermentation of Primitivo grapes, which were collected from the vineyards of three different cellars. The three selected starters (one for each cellar) were tested during fermentations at pilot scale by performing in each cellar two trials: one with an indigenous starter (specific for the winery), and one with the commercial starter AWRI796 (common to all the cellars). Starter dominance ability and influence on aromatic quality of the wine were used as criteria to test the suitability of these indigenous starters to be used at the cellar scale. The results obtained in this study showed that the indigenous strains were characterized by very high dominance ability, and the aromatic quality of wine was strongly influenced both by the inoculated strain and the interaction strain/grape must.
... The total protein content was estimated by the standard Biuret assay method using Bovine serum albumin (BSA) of 10 mg/ml stock as standard [24]. Total acidity and volatile acidity was determined by titration of the samples against sodium hydroxide solution using phenolphthalein as indicator and expressed as grams of tartaric acid present per 100 ml of the samples and grams of acetic acid present per 100 ml of the samples [25]. Alcohol percentage of the non-distilled rice beer was determined by titration of the samples against sodium thiosulphate solution using dichromate oxidation method and expressed in percentage volume by volume [26]. ...
... They are secondary metabolites formed in grape berries and accumulated as non-volatile sugar-bound conjugate forms (glycoconjugates). Glycoconjugates can be hydrolysed during the alcoholic fermentation by acid-catalysed hydrolysis or by β-glycosidase enzymes coming from grapes and/or from wine yeasts (Ugliano, Bartowsky, McCarthy, Moio, & Henschke, 2006;Ugliano & Moio, 2008). Five monoterpene compounds were determined in control wines during both vintages (linalool, α-terpineol, β-citronellol, geraniol, and p-cymene). ...
The impact of fungicides mepanipyrim (Mep) and tetraconazole (Tetra) and their corresponding commercial formulations (Mep-Form and Tetra-Form) on the aroma composition of wines was assessed. Fungicide residues can affect the biotransformation of aroma precursors from grapes and/or the yeast metabolism. The results confirmed that both maximum residue levels (MRL and 2xMRL) of Mep promoted benzyl alcohol and 4-vinylguaiacol contents; while MRL and 2xMRL of Mep-Form promoted benzene derivatives (benzyl alcohol, benzaldehyde, and trans-isoeugenol), 2-phenylethanol and γ-nonalactone. The addition of Tetra (2xMRL) and Tetra-Form (MRL and 2xMRL) release higher contents of cis-3-hexen-1-ol and ethyl vanillate and affected yeast metabolism related to phenylacetaldehyde, 2-phenylethanol, methionol, capric acid, ethyl 2-methylbutyrate, ethyl isovalerate, ethyl monosuccionate, diethyl succinate and γ-butyrolactone production. Fungicide residues did not display higher variations in global odour activity values with respect to control wines, although some variations on the "floral", "fruity", "spicy" and "lactic" nuances could be sensed.
... With the exclusion of vanillin, the concentration of all these compounds was found to change remarkably with fermentation, in particular in the case of linalool, β-damascenone, and ethyl vanillate. In the case of linalool, this increase is consistent with previous observations indicating that the majority of linalool in wine from non-aromatic grapes arises from yeast-driven hydrolysis of glycosidic precursors (Ugliano, Bartowsky, McCarthy, Moio, & Henschke, 2006). Likewise, β-damascenone accumulates largely during fermentation, mostly due to yeast-driven reduction of the ketonic group of certain grape derived megastimane norisprenoids and subsequent acid rearrangements (Lloyd et al., 2011). ...
In this study, the diversity existing at the very small scale of single vineyard parcels in volatile composition of grapes and wines from a single estate in the Valpolicella wine region has been studied. Corvina grapes from eight contiguous vineyards were used for the study and vinified with the same protocol. The compounds analyzed by GC-MS were representative of the terpenoid, norisoprenoid and benzenoid chemical families. Free and bound compounds analysis showed that differences between parcels were relatively small on grapes samples, whereas after fermentation larger differences between wine samples were highlighted. Multivariate statistical analysis of wine volatiles highlighted the existence of similarities between wine volatile profiles, which reflected to a good extent the geographical location of the corresponding vineyard parcels. The main drivers of this diversity were the monoterpene alcohols linalool, α-terpineol, linalool oxide; the benzenoids vanillin, ethyl vanillate and methyl vanillate; and the norisoprenoid β-damascenone. Wine from one vineyard parcel was not correctly classified, possibly due to the influence of the peculiar training system applied to this parcel. With aging the vineyard parcel geographical diversity was still reflected by the chemical diversity of wines, even if the separation was less fine. As many reactions occurred, some drivers of the diversity were changed after aging. They were benzenoids: ethyl vanillate, methyl vanillate and vanillin; the norisoprenoid 3-oxo-α-ionol; the terpenes linalool oxide, linalool, p-methane-1,8-diol, α-terpineol, and the precursors of nerol, geraniol, linalool.
In this chapter, we attempt to bring together in a readable and accessible form the wine volatiles patterns highlighting, in a comprehensive way, their differentiated origins. In this context, it is aimed to describe the volatile compounds i) biosynthesized in the grapes few of them are responsible for the impact aroma of some grape varieties and wines, such us monoterpenes, thiols, and pyrazines, that persist unchanged into wine; ii) the originated during the alcoholic fermentation through fermenting yeasts metabolism, enzymatic reaction and lactic acid bacteria action, and from transformation of grape-specific precursors, namely alcohols, ethyl and alkyl esters, aldehydes, and fatty acids, which contribute substantially to the flavor and to the base wine aroma, and iii) the volatiles formed during the wine storage and/or aging through several chemical reactions, including redox phenomena, Maillard reactions, and Strecker degradation, abiotic transformation of precursor compounds in wine, microbial spoilage, and difusion from oak, from which we can highlight the furanic compounds, lactones and acetals (dioxanes and dioxolanes), among others. The most important and dominant volatile compounds derived from these three main pathways are discussed in some detail.
This work studies the variability of the Saccharomyces cerevisiae present during the spontaneous fermentation of Garnacha grapes’ musts from a “Pago” winery from the east of Spain. The parameters used to select yeast are those related to growth, fermentative behaviour, and the influence on the wine’s aroma and polyphenolic composition. Yeast identification was performed by ITS analysis and typed by Hinfl mDNA restriction profile analysis. Growth and metabolic characteristics of the isolates were determined by laboratory-scale fermentations of sterile Garnacha must, and the composition of the polyphenolic and the volatile compounds, and the sensory attributes of the small-scale produced red wines were determined. Ten S. cerevisiae strains were isolated and characterized. Overall, strain 22H quickly grew, produced wines with moderate ethanol concentrations and low volatile acidity, and obtained the highest colour and aroma scores, plus a high score for sensory attributes.
Yeast co-inoculations in winemaking are often studied in the framework of modulating the aromatic profiles of wines. Our study aimed to investigate the impact of three cocultures and corresponding pure cultures of Saccharomyces cerevisiae on the chemical composition and the sensory profile of Chardonnay wine. Coculture makes it possible to obtain completely new aromatic expressions that do not exist in the original pure cultures attributed to yeast interactions. Esters, fatty acids and phenol families were identified as affected. The sensory profiles and metabolome of the cocultures, corresponding pure cultures and associated wine blends from both pure cultures were found to be different. The coculture did not turn out to be the addition of the two pure culture wines, indicating the impact of interaction. High resolution mass spectrometry revealed thousands of cocultures biomarkers. The metabolic pathways involved in these wine composition changes were highlighted, most of them belonging to nitrogen metabolism.
Saccharomyces yeasts from different origins and species fermented in a semi-synthetic must containing aroma precursor of cv. Albariño and polyfunctional mercaptans precursors. The resulting wines were subjected to accelerate anoxic aging. Afterward, aroma profiles were analyzed by distinct gas chromatography methodologies.
Cryotolerant strains showed better fermentation performances with significant differences in volatile and non-volatile fermentation products than Saccharomyces cerevisiae (S. cerevisiae). We suggested that the highest levels γ-butyrolactone and diethyl succinate in Saccharomyces uvarum (S. uvarum) strains, together with their substantial succinic acid yields, could be related to greater flux through the GABA shunt. These strains also had the highest production of β-phenylethyl acetate, geraniol, and branched-chain ethyl esters. The latter compounds were highly increased by aging, while acetates and some terpenes decreased. S. kudriavzevii strains showed a remarkable ability to release polyfunctional mercaptans, with SK1 strain yielding up to 47-fold and 8-fold more 4-methyl-4-mercaptopentan-2-one (4MMP) than S. cerevisiae and S. uvarum strains, respectively. The wild S. cerevisiae beer isolate showed a particular aroma profile due to the highest production of ethyl 4-methylvalerate (lactic and fruity notes), γ-octalactone (coconut), and furfurylthiol (roasted coffee). The latter compound is possibly produced from the pentose phosphate pathway (PPP). Since erythritol, another PPP intermediate was largely produced by this strain.
Ферментированные яблочные напитки производятся во всем мире с различным физико-химическим составом и органолептическими показателями. Несмотря на имеющиеся различия производители сидра сталкиваются с аналогичными проблемами и рисками. Основное влияние на процесс брожения сидра оказывает физико-химический состав сырья. Следовательно, для производства сидра хорошего качества требуется сырье определенного химического состава. Кроме того дрожжи и продукты их метаболизма являются важными факторами в процессе брожения. Производители сидра и других алкогольных напитков в постоянном поиске новых штаммов дрожжей для производства «аутентичных» и разнообразных напитков, которые отличаются друг от друга и в итоге должны привлечь большее количество потребителей. Исследовательских материалов о производстве сидра намного меньше по сравнению со статьями о производстве вина, особенно о влиянии химического состава яблок и его микробного разнообразия на процесс ферментации. Несмотря на то, что переработка ферментированных напитков мало отличается с точки зрения микробиологии и производства, изучение конкретных свойств сырья и производственных проблем при производстве сидра является полезным и значимым для производителей сидра. В этом обзоре обобщены научные публикации о химическом составе яблок, влиянии состава сусла на процесс брожения и рост дрожжей. Кроме того, рассматривается микробное разнообразие сидра, микробиологическая активность и ее влияние на ферментацию. Сведения о химическом составе различных сортов, в частности содержании сахаров, органических кислот, соединений азота и полифенолов, имеет важное значение, поскольку они напрямую влияют на процесс брожения и органолептические показатели производимых сидров.
Wine has very rich and complex aromas but is paradoxically obtained from grape juice that has very little odor itself. This aromatic transformation is mainly due to the action of yeasts during the alcoholic fermentation. First, yeasts produce secondary metabolites that give to wines its basic “winy” characteristic. Second, some enzymatic activities may transform nonodorous compounds of certain grape varieties into varietal aromas, giving the specific characteristics of “cépage.” Depending on the yeast strain, the concentration of aromatic molecules is determined, modifying the organoleptic perception of wine. The enzymatic activities of yeast metabolism and their genetic control have been widely studied, allowing genetic selection approaches as well as molecular engineering for selecting more specialized commercial starters.
This study analyzed the microbiomes of 23 Chinese koumiss samples using deep metagenomic sequencing, as well as metagenome datasets of 20 nunu, 18 kefir, and 12 yogurt samples retrieved from public genome databases. There were large variations in the microbiota composition between sample types, reflected by the great differences in their profiles of dominant species. One-hundred fifty-three metagenome-assembled genomes were assembled, including four novel species belonging to the Lactobacillus, Streptococcus, Acetobacter, Rothia genera. The novel genomes contained various gene elements, encoding carbohydrate-active enzymes, secondary metabolite clusters, and bacteriocins, which might influence food flavor, quality and/or safety. Bacteriocin-encoding genes were common, which might help control undesirable microorganisms. Our metagenomic analysis also revealed the content of bacteriophage sequences of these products, meanwhile uncovering complex interactions between fermented milk-associated bacteriophages and bacteria, including the history of bacterio-phage infection and relationship between Lactobacillaceae and bacteriophages. This study highlighted the microbial diversity and heterogeneity across fermented milk products. Our data demonstrated the power of deep metagenomic sequencing in expanding our understanding of low-complexity microbial communities.
Aroma profiles of withered Corvina and Corvinone wines from two different Valpolicella terroirs were investigated in relationship to yeast strain and use of spontaneous fermentation. The results indicated that volatile chemical differences between wines were mainly driven by grape origin, which was associated with distinctive compositional profiles. Wine content in terpenes, norisoprenoids, benzenoids and C6 alcohols, as well as some fermentative esters, were indeed significantly affected by grape origin. Conversely, yeast strain influence was mainly associated with fermentation-derived esters. Sensory analysis, besides confirming the major role of grape origin as driver of wine differentiation, indicated that spontaneous fermentations reduced the sensory differences associated with grape origin and variety, mainly due to high content of acetic acid and ethyl acetate.
Background and Aims
Terpenes are major varietal aroma compounds significantly contributing to wine quality and style. Autochthonous microbial starters can promote the formation and release of the terpenes and thus highlight the terroir typicality of wines. This study compared the physicochemical parameters, changes in the terpene concentration, β-D-glucosidase activity and sensory attributes of Chardonnay wines fermented individually by the Saccharomyces cerevisiae autochthonous MQ3 strain isolated from spontaneous fermented grape must and by three commercial S. cerevisiae strains.
Methods and Results
The evolution of terpenes during alcoholic fermentation was followed with ultrasound-assisted liquid–liquid extraction combined with GC. The physicochemical parameters of wine fermented by the MQ3 strain were significantly different from those of the wines fermented by other yeasts. The pattern of the terpenes detected, including linalool, α-terpineol, farnesol, geraniol, nerol and citronellol, varied during alcoholic fermentation. The MQ3 strain induced greater accumulation of terpenes with increased concentration of α-terpineol, geraniol and (E,E)-farnesol. Besides, the MQ3 strain exhibited an enhanced ability to produce β-D-glucosidase compared to that of the other three strains. With the exception of α-terpineol and (E,E)-farnesol, there was no significant correlation between the concentration of the other terpenoids and β-D-glucosidase activity as shown by Pearson's correlation analysis. Wine produced with the MQ3 strain was characterised by a distinctive complex flavour with enhanced floral and fruity aromas.
Conclusions
The autochthonous MQ3 strain had a positive effect on the varietal aroma and sensory quality of the wines.
Significance of the Study
Due to its aroma enhancing ability, the MQ3 strain could be applied to produce quality Chardonnay wine with terroir typicality.
Beta-glucosidase is an important enzyme for the hydrolysis of grape glycosides in the course of winemaking. Yeasts are the main producers of β-glucosidase in winemaking, therefore play an important role in determining wine aroma and flavour. This article discusses common methods for β-glucosidase evaluation, the β-glucosidase activity of different Saccharomyces and non- Saccharomyces yeasts and the influences of winemaking conditions, such as glucose and ethanol concentration, low pH environment, fermentation temperature and SO2 level, on their activity. This review further highlights the roles of β-glucosidase in promoting the release of free volatile compounds especially terpenes and the modification of wine phenolic composition during the winemaking process. Furthermore, this review proposes future research direction in this area and guides wine professionals in yeast selection to improve wine quality.
Terpenes significantly affect the flavor and quality of grapes and wine. This review summarizes recent research on terpenoids with regard to grape wine. Although, the grapevine terpene synthase gene family is the largest identified, genetic modifications involving terpenes to improve wine flavor have received little attention. Key enzyme modulation alters metabolite production. Over the last decade, the heterologous manipulation of grape glycosidase has been used to alter terpenoids, and cytochrome P450s may affect terpene synthesis. Metabolic and genetic engineering can further modify terpenoid metabolism, while using transgenic grapevines (trait transfer to the plant) could yield more flavorful wine. We also discuss traits involved in wine aroma quality, and the strategies that can be used to improve grapevine breeding technology.
This chapter contains sections titled: Introduction Definition of Asava and Arishta Method of Preparation for Asava Arishta Role of Ingredients and Process Advantages of Asava–Arishta Over Other Dosage Form Future Perspective Acknowledgements
Yeast had participated with humans in food fermentation since the production of wine and bread, more than 10,000 years of shared history. It is well understood that fungi diversity is still underestimated and that we are far from understanding its importance and potential impact in biotechnology. Flavor compounds as “secondary metabolism” are very sensitive to fermentation conditions and mixed cultures, and although we had experience an exponential development of molecular biology in the last 30 years, metabolomics is still in its infancy. It was demonstrated in recent years that increase strain and species yeast diversity in a fermentation system increases sensory complexity and chemical aroma compound diversity in the final fermented product. Flavor compounds had many key functions for yeast, such as for survival and dispersion strategies, pheromone and defense mechanisms, and “quorum sensing” mechanisms for cell communication. Humans had taken advantage of many of these functions to increase taste and food sensory pleasure for a more exigent consumer, a phenomenon called “yeast domestication.” We focus this chapter mainly in the recent discussed yeast synthetic pathways for the formation of phenylpropanoid and terpenoid aroma compounds. In addition, we will emphasize the current knowledge that grape and wine microbiology research has contributed to understand how complex natural and inoculated yeast flora can affect flavor quality. The flavor phenotype concept and how to screen natural flora and develop consortia starters to innovate in food biotechnology are discussed.
p style="text-align: justify;">Osidases located in periplasmic space of Saccharomyces cerevisiae are able to hydrolyse monoterpenes heterosides of Muscat grapes. To prepare the periplasmic extract, yeast cell walls are digested with Zymolyase in the presence of an osmotic protector to prevent lysis of the resulting protoplasts; periplasmic enzymes are liberated into the supernatant medium. Monoterpenes heterosides are incubated 48 or 72 hours at 25° C with either intact yeast cells or periplasmic enzymatic extract. Monoterpenes, especially gerianol and nerol, are liberated in these conditions. β-glucosidase activity seems to play an important rôle in these reactions.
Fungal extracellular β-glucosidases are commonly strongly inhibited by glucose. Surprisingly, the activity of periplasmic yeast β-glucosidase is quite glucose independant. These results suggest that some periplasmic enzymes from yeast may be involved in the hydrolysis of varietal aroma precursors in wines.</p
La formation du citronellol à partir du géraniol et du nérol au cours de la fermentation de moûts synthétiques et naturels de raisin par différentes souches de levures a été étudiée. Le géraniol et le nérol sont transformés en citronellol par la levure, ceci de façon plus marquée avec le géraniol. La quantité de citronellol formé dépend de la souche de levure utilisée. D'autres monoterpènes, comme les acétates de géranyle et de néryle et l'α-terpinéol, sont aussi formés au cours de la fermentation. La préparation enzymatique utilisée n'a pas montré d'activités réductases vis-à-vis du géraniol et du nérol pour former du citronellol.
L'action des glycosidases exogènes d'origine fongique (α-arabinosidase, α-rhamnosidase, β-apiosidase, β-glucosidase) a été étudiée en vinification en vin doux naturel (VDN) et en vin sec du moût de Muscat de Frontignan. La teneur en fraction libre de l'arôme a montré une forte augmentation dans le cas du vin sec issu du moût enzymé : d'une part la concentration en certains terpénols (nérol, géraniol, citronellol, α-terpinéol, hydroxylinalols) a sensiblement augmenté, d'autre part des composés nor-isoprénoïdiques (β-damascénone, 3- hydroxy-β-damascone), intéressants sur le plan olfactif, ont apparu. On a démontré que l'augmentation de la concentration de la plupart des composés aromatiques était le résultat de l'action hydrolytique des glycosidases exogènes sur les précurseurs glycosidiques. Le vin sec issu du moût enzymé a été jugé plus aromatique (floral) et plus typé. Dans le cas du VDN issu du moût enzymé, l'hydrolyse des précurseurs glycosidiques d'arôme a été interrompue au stade de monoglucosides, dû à l'inhibition de l'activité β-glucosidase par la présence du glucose. Ainsi la fraction libre de l'arôme n'a pu augmenter comme dans le cas du vin sec enzymé.
Background and Aims: The aim of this work was to establish a general method for evaluating the intrinsic activity of yeasts towards the release of volatiles terpenes from glycosidic aroma precursors. Methods and Results: The enzymatic capacity of yeast cells towards glycosidic aroma precursors was assessed on permeabilised yeast cells. In this way, the pores created into the cell membrane allowed the precursors to freely enter the cells. Conclusions: The comparison between the release of terpenes from glycosidic aroma precursors by entire viable cells during fermentation and by permeabilised cells shows that the permeation of glycosidic aroma precursors through the yeast cell membrane is the main bottleneck for such release. Significance of the Study: This work highlights the fact that Saccharomyces species can exhibit β-glycosidase activity as high as non-Saccharomyces species. This important result points out future prospects for the improvement of Saccharomyces species by classical genetics.
Volatile compounds released from Cabernet Sauvignon and Merlot grape glycoside fractions, isolated from both skin and juice, were studied by sensory descriptive analysis and by gas chromatography-mass spectrometry (GC-MS). Both acid- and enzyme-hydrolysates were studied. The contribution to wine aroma of the different fractions was evaluated by sensory analysis of white wines to which the hydrolysates had been added. Acid-hydrolysates from each variety increased the intensity of attributes such as tobacco, chocolate and dried fig. In contrast, glycosidase enzyme-hydrolysates gave no detectable change in aroma. The relationship among the aroma attributes of the hydrolysates and their volatile composition was investigated using partial least square regression analysis (PLS), which indicated that the intensity of the attributes dried fig, tobacco and honey could be related to the concentration of specific compounds of the norisoprenoid, benzene derivative, monoterpene and aliphatic classes. The red-free glycosyl-glucose (G-G) concentration of the skin extracts and juices was correlated with the scores of aroma attributes of the glycoside hydrolysates, suggesting the potential of the G-G assay as a predictor of wine aroma.
The development of the aromas of certain grapes varieties during fermentation has not been greatly investigated in enology until now. Recent works on sulfur compounds that participate in the aroma of Sauvignon blanc wines offer an example of grape flavor enhancement by yeasts. Several very odorous volatile thiols have been identified as constituents of the particular aroma of Sauvignon blanc wines: 4-mercapto-4-methylpentan-2-one (4MMP), 4-mercapto-4-methylpentan-2-ol, 3-mercaptohexanol, 3-mercaptohexyl acetate. These different thiols are practically absent in grapes or musts. They appear in wines during the alcoholic fermentation. This increase in varietal flavor due to yeast metabolism can be explained by the degradation of S-cysteine conjugates in the grape, leading to the formation of corresponding volatile thiols. The ability of Saccharomyces cerevisiae strains to augment Sauvignon blanc aromas related to these sulfur-containing aroma compounds is variable. The same Sauvignon must fermented by pure cultures of different yeast strains results in wines with different levels of volatile sulfur aromas. Certain yeast strains (EG8, VL3c) which winemakers have empirically noted produce Sauvignon wines with pronounced varietal character, release the largest quantities of 4MMP. The differences in behavior between S. cerevisiae strains also appears during the fermentation of model mediums added with S-4-(4-methylpentan-2one)-L-cysteine. Comparing the S. cerevisiae strains commonly used in winemaking, certain wild varieties of Saccharomyces bayanus have been proved particularly suited to freeing the Sauvignon sulfur aromas. Such strains have been isolated in spontaneous fermentation in Sancerre. Natural hybrids between S. cerevisiae and S. bayanus var. uvarum have also been found. They may also be obtained in the laboratory by breeding. The interest in the interspecific hybrids for the vinification of certain grape varieties must be examined.
Four strains of Saccharomyces cerevisiae were evaluated for their influence on White Riesling glycoconjugates. Fermentation resulted in a decrease in bound glycosides, as estimated by the analysis of glycosyl glucose. The greatest reduction occurred with the Fermiblanc strain, although the maximum difference among yeasts was only 7%. The concentration of bound monoterpene alcohols, oxides, and aromatic alcohols was diminished due to fermentation, although generally similar among yeasts. Following fermentation, the concentration of free terpenes and aromatic alcohols differed slightly among yeasts, but differences were below the sensory thresholds reported for each compound. Post-fermentation thermal processing reduced the glycoconjugates by an average of 33% for all treatments, with the greatest reduction occurring with the VL1 strain. Storing wines for 45 days sur lie lessened the glycoside content uniformly among treatments by 52%.
Volatile components liberated by hydrolysis of C-18 reversed phase isolates from Vitis vinifera cv. Shiraz juice were evaluated by sensory descriptive analysis. The isolates were hydrolyzed at pH 3.2 or by treatment with a non-selective glycosidase enzyme. Shiraz juices assigned as high and low 'quality', each sourced from two regions and sampled in 1988 and 1989, were studied. Wines made from the 1989 juices were also subjected to descriptive analysis. The results showed that for one pair of wines and all but one pair of hydrolysates, the quality differences could be distinguished and quantified. The glycosidic hydrolysates prepared by both methods were found to contribute non-berry attributes to wine such as 'stalky', 'earthy', and 'cigar/tobacco'. Wines considered to be of high quality were rated higher in these non-berry attributes than their low quality counterparts, and it may be deduced that glycosidic hydrolysates contain aroma compounds that are important to high quality Shiraz wine.
The stability of free and glycosidically-bound fractions of some components of Muscat grape aroma (terpenols and aromatic alcohols) was investigated during alcoholic fermentation and in wines of different ages. Some free terpenols, such as linalool, vary little during fermentation; for others, such as geraniol, the decrease is considerable. Hydrolysis of bound terpenols is low. During wine aging, and depending on the different terpenols, slow hydrolysis of terpenoid glycosides seems to occur in wine. Free linalool and [agr]-terpineol increased while geraniol and nerol decreased in older wines.
The precursors of vitispirane (two diastereoisomers), 1,1,6-trimethyl-l,2-dihydronaphthalene (TDN), damascenone, and a fourth unknown volatile norisoprenoid in Riesling wine were analyzed by droplet counter-current chromatography (DCCC). The volatile compounds were monitored by GC-MS after mild acid hydrolysis of pooled DCCC fractions. Each of the four volatiles was derived from several precursors. The precursors appear to include glycoconjugates involving different conjugating moieties and also non-glycosidic compounds. The vitispiranes and damascenone are each produced from at least two aglycons which, in turn, are variously glycosylated. Consequences are discussed for the existence in grapes and wines of multiple precursors of the volatile flavor compounds, and a rapid method for assessing bottle aging potential of wines is suggested
Four strains ofSaccharomyces cerevisiaeand native yeasts were evaluated for their influence on White Riesling-conjugated aroma precursors, which were measured using three analytical procedures. Fermentation resulted in a decrease in glycosyl glucose with the greatest reduction occurring with native yeast fermentations. Potentially volatile terpene levels were similar among wines following fermentation, the exceptions being those fermented using the Fermiblanc strain and native yeasts which showed lower concentrations. Storing wines for 45 days on the yeast lees (sur lie) reduced the glycosyl glucose and potential volatile terpene content with slight differences among treatments. Gas chromatographic analysis of selected glycosidically bound monoterpene alcohols, oxides, and aromatic alcohols showed a trend similar to the glycosyl glucose and potentially volatile terpenes following fermentation. Fermentation had a variable effect on the free linalool concentration. Levels of nerol and geraniol decreased while free α-terpeniol, hotrienol, furanic and pyranic linalool oxides, benzyl alcohol, and 2-phenylethanol increased. The concentrations of free volatiles following fermentation differed among yeasts, but differences were below the sensory thresholds reported for each compound.
β-glucosidase activity of differentSaccharomycesstrains has been detected on the basis of its hydrolytic activity onpara-nitrophenyl-β-glucoside (pNPG) and terpene glycosides of Muscat wine. This enzymatic activity is induced by the presence of boundβ-glucose as the only carbon source in the medium and seems to be a characteristic of the yeast strain.β-glucosidase is associated with the cell wall and is found in the insoluble fraction obtained from lysed yeast cells.Saccharomyces β-glucosidase is quite glucose independent, so that its activity is reduced by about 40% in the presence of 200 g/l of glucose, but it is inhibited by about 50% with 5% ethanol in the medium; therefore, its technological use seems to be restricted to the first stages in the wine-making process.
I. ROSI, M. VINELLA AND P. DOMIZIO. 1994. Three hundred and seventeen strains representing 20 species of yeasts were screened for the presence of β-glucosidase activity. All of the strains of the species Debaryomyces castellii, Deb. hansenii, Deb. polymorphus, Kloeckera apiculata and Hansenula anomala showed β-glucosidase activity, but only one of 153 strains of Saccharomyces cerevisiae. The other species behaved differently, depending upon the strain. The strains that hydrolysed arbutin were checked to localize the β-glucosidase activity. A strain of Deb. hansenii exhibited the highest exocellular activity and some wall-bound and intracellular activity. The β-glucosidase synthesis from this yeast was enhanced by aerobic conditions of growth, was repressed by high glucose concentration (9%) and occurred during exponential growth. The optimum conditions for enzymatic preparations of Deb. hansenii were between pH 4.0 and 5.0 and 40d̀C. A high concentration of ethanol and glucose did not reduce the ezymatic activity. The enzymatic preparations of Deb. hansenii released monoterpenols and other alcohols from a grape glycoside extract.
Three hundred sixty-one yeast strains (80 of which ascribable to Saccharomyces cerevisiae) were isolated from Sicilian musts and wines with the purpose of looking for β-glucosidase (βG, EC 3.2.1.21) activity. Of these, the AL 41 strain had highest endogenous βG activity and was identified as belonging to the species S. cerevisiae by biochemical and molecular methods. This enzyme was subsequently characterized. It had optimum effect at pH 3.5–4.0, whilst optimum temperature was 20°C, compatible with typical wine-cellar conditions; it was not inhibited by ethanol, at concentrations of 12–14%, or fructose and glucose. The βG was also characterised in terms of the kinetic parameters Km (2.55mM) and Vmax (1.71Umg−1 of protein). Finally, it remained stable for at least 35 days in model solutions of must and wine.
Falanghina must was clarified through five methods: spontaneous settling (SS); spontaneous settling with addition of pectic enzyme (E); filtration of E (EF); fining of E with bentonite, casein, silica gel, and charcoal (EC); and EC treatment followed by filtration (ECF). The concentration of free varietal aroma compounds and glycoconjugates was then investigated. Clarification procedure did not affect the concentration of must-free terpenols,
while a positive correlation was found between the intensity of prefermentative clarification and the content of glycoconjugates of must, as measured by glycosyl-glucose, with a trend of SS > E = EF > EC = ECF. Glycosylated precursors of linalool, geraniol, benzyl alcohol, 2-phenylethanol, and eugenol were significantly decreased by must clarification. In all treatments, fermentation resulted in a large decrease in bound geraniol, benzyl alcohol, and 2-phenylethanol. The decline of bound linalool and eugenol was smaller and varied according to yeast strain and treatment. Only free forms of linalool and benzyl alcohol were significantly increased by fermentation. Since musts with lower contents of glycosylated precursors resulted in wines with lower levels of both these compounds and of some volatiles potentially resulting from their hydrolysis, prefermentative clarification may influence both expression of varietal character and aging potential of Falanghina wine.
Forty-four odor-active compounds were quantified in Scheurebe and Gewürztraminer wines, respectively. Calculation of odor activity values (OAVs) of odorants showed that differences in odor profiles of both varieties were mainly caused by cis-rose oxide in Gewürztraminer and by 4-mercapto-4-methylpentan-2-one in Scheurebe. On the basis of their high OAVs, ethyl octanoate, ethyl hexanoate, 3-methylbutyl acetate, ethyl isobutyrate, (E)-β-damascenone, and 3a,4,5,7a-tetrahydro-3,6-dimethylbenzofuran-2(3H)-one (wine lactone) were further potent odorants in both varieties. The compounds were dissolved in a water/ethanol mixture in various combinations and in concentration levels equal to those in wine. The results indicated that the aromas of Gewürztraminer and Scheurebe models were in good agreement with the original wines. Keywords: Gas chromatography; stable isotope dilution assay; quantitation; white wine; Gewürztraminer; Scheurebe
Free and bound aroma compounds of eight Spanish grape cultivars (Albariño, Treixadura, Listan, Viura, Xarel.lo, Parellada, Garnacha, and Tempranillo) used in winemaking were studied. With a single-extraction procedure it was possible to provide information about the potential flavor of these varieties: bound aroma was determined directly by TFA glycoside analysis and indirectly by enzyme hydrolysis release of aglycon. An aroma data base of these varieties and a comparison between the grape flavor composition of each variety were established. Grape characteristics (sugars, acidity, polyphenols, juice yield), mainly due to climate and cultivar factors, were related with the aroma composition. Non-terpenyl compounds such as 2-phenylethanol and benzyl alcohol were the main glycosidically bound compounds of Spanish varieties. Direct determination of glycosides is better than hydrolysis of aglycon as an approach to the potential aroma of grapes. Keywords: Aroma; glycosides; Spanish grape cultivars; Albariño; ’Treixadura; Listan; Viura; Xarel.lo; Parellada; Garnacha; Tempranillo
Carbohydrate and aglycon moieties released, respectively, by acid and enzymatic hydrolysis of African mango pulp extracts containing glycosidically bound compounds were identified by TLC, GC, and GC/MS. Glucose was found to be the most important sugar constituent of the glycoside saccharidic moiety, while significant amounts of arabinose and trace amounts of rhamnose were detected. Several aglycons [(Z)-hexen-3-ol, hexanol, hexanoic acid, 2,5-dimethyl-4-hydroxy-3-(2H)furanone (furaneol), linalool oxides, α-terpineol, carvacrol, vanillin, cis- and trans-6-p-menthen-2,8-diol, 1,8-p-menthadien-7-ol, 1-p-menthen-7,8-diol, and 9-hydroxymegastima-4-en-3-one] were identified as additional mango bound volatile compounds. Fatty acids (myristic and stearic acids) were also found in glycosidically bound form. Ten glycosides (benzyl, 2-phenylethyl, and α-terpineyl glucosides and rutinosides, eugenyl, vanillyl and furaneyl glucosides and α-terpineyl arabinoglucoside] were identified for the first time in mango by GC/MS of trifluoroacetylated derivatives and GC using reference compounds. Linalyl oxide glucosides (four isomers) and C13 norisoprenoid derivatives [9-hydroxymegastima-4,6-dien-3-one (two isomers), 9-hydroxymegastima-4,7-dien-3-one, and vomifoliol glucosides and arabinoglucosides] were tentatively identified. Keywords: Mango; glycosidically bound compounds; TFA derivatives; GC/MS
Thermal induction of volatile monoterpenes in juices of muscat grapes (sp. Vitis vinifera cv. Muscat of Alexandria and Muscat à Petits Grains) was studied by GC and GC-MS of headspace samples. The roles of the four recently discovered grape polyols 3,7-dimethylocta-1,5-diene-3,7-diol (1), 3,7-dimethylocta-1, 7-diene-3,6-diol (2), 3,7-dimethyloct-1-ene-3,6,7-triol (3), and 3,7-dimethyloct-1-ene-3,7-diol (4) are interpreted in this process. Heating juice for 15 min at 70 °C significantly increased the concentration of the furan linalool oxides, nerol oxide, hotrienol, and α-terpineol. Also 2,6,6-trimethyl-2-vinyltetrahydropyran, cis- and trans-5-isopropenyl-2-methyl-2-vinyltetrahydrofurans, 2,2-dimethyl-5-(1-methylpropenyl) tetrahydrofuran, myrcenol, and cis- and trans-ocimenols, all previously unrecognized as grape products, became prominent constituents of heated juice headspace composition. Under mild acid conditions at grape juice pH, polyols 1-4 rearranged nonenzymatically, to give all of the above volatile products.
Acuminoside (geranyl 6-O-β-D-apiofuranosyl-β-D-glucopyranoside) has been characterized in Vitis vinifera vars. Muscat of Frontignan, Muscat of Alexandria, Muscat Ottonel, Muscat of Hambourg, and Gewürztraminer. Moreover, similar disaccharide glycosides of monoterpenols, of 2-phenylethanol, and of benzyl alcohol were tentatively identified on the basis of the GC-EIMS and GC-CIMS of their trimethylsilyl and trifluoroacetyl derivatives.
Geosmin is responsible for natural flavors in beans and beets and for off-flavors in water and fish. This tertiary decalol reacts with bromine in the presence of formic acid to produce a blue complex with maximum absorbance at 650 nm. A method for carrying out this reaction is described, and a possible mechanism is discussed.
The efficiency of hydrolysis of monoterpenyl β-D-glucosides by various plant (grape and sweet almond) and fungal (Aspergillus niger) β-glucosidases was found to be dependent on the structure of the aglycon and the origin of the enzyme. Plant β-glucosidases hydrolyzed only β-D-glucosides of primary alcohols, such as geraniol, nerol, and citronellol. β-D-Glucosides of tertiary alcohols such as linalool and α-terpineol could be hydrolyzed efficiently only by one of the two fungal β-glucosidases studied. Diastereoisomeric monoterpenyl β-D-glucosides (linalool, α-terpineol, citronellol) and isomeric monoterpenyl β-D-glucosides (geraniol, nerol) were hydrolyzed at different rates.
The β-D-glucopyranoside and the 6-O-α-arabinofuranosyl-β-D-glucopyrano8ide of (E)-2,6-dimethylocta-2,7-diene-1,6-diol were isolated from Vitis vinifera cv. Riesling grape juice and their structures determined by spectral methods. Additionally, the diastereoisomeric 3,7-dimethylocta-1,6-diene-3,5-diols and (E,E)-2,6-dimethylocta-2,6-diene-1,8-diol were identified for the first time in grapes, and these three diols together with (E)- and (Z)-2,6-dimethylocta-2,7-diene-1,6-diol were quantified both as free monoterpenes and as glycosides in the juice of eight grape varieties. Model experiments were carried out on (E)-2,6-dimethylocta-2,7-diene-1,6-diol and the 3,7-dimethylocta-1,6-diene-3,5-diols to assess their roles as potential precursors of flavorants in juice and wine. The first compound, although largely resistant to acid hydrolysis, yielded (E,E)-2,6-dimethylocta-2,6-diene-1,8-diol as the major product and p-menth-1-en-9-al and 3,9-epoxy-p-menth-1-ene as trace products. The mixture of 3,7-dimethylocta-1,6-diene-3,5-diols decomposed to give (E)-2,6-dimethylocta-3,7-diene-2,6-diol, hotrienol, and nerol oxide, all of which are known wine components.
An analytical assay for glycosylated secondary metabolites of grapes, juices and wines, through quantification of glycosyl glucose (G-G), has been optimized and validated. The glycosides are isolated on Cls reversed-phase silica gel and hydrolyzed with sulfuric acid at 100 degrees C; the released glucose is determined enzymatically. The accuracy and precision of the assay, determined from the gradients and coefficients of determination of linear regression curves for the recovery of a standard glycoside from wine, juice or homogenized fruit extract ranged, respectively, from 0.957 to 1.021 and from 0.991 to 0.997. Some examples of application of the assay are presented-the decrease of G-G in wines with aging, the range of G-G in Shiraz juices from different regions, and the development of G-G in ripening fruit.
The aroma properties of hydrolysed glycosidic precursors from Semillon, Sauvignon Blanc and Chardonnay grape juices were investigated in a neutral wine medium using sensory descriptive analysis. The glycosidic fractions were hydrolysed by acid catalysis in the presence or absence of ethanol, by glycosidase enzyme action, or by a sequence of glycosidase and acid treatments. Wines made from the Chardonnay and Semillon juices were also assessed. Sensory difference tests showed that samples from each variety for each treatment were distinct, except the hydrolysates prepared enzymically from Semillon and Chardonnay. The aroma of each acid hydrolysate was distinguishable from the neutral wine by enhanced intensity of the attributes honey, tea, lime and floral. Enzyme treatment of the glycosides from Sauvignon Blanc gave a hydrolysate with aroma properties similar to those of the corresponding acid hydrolysate, but with less intense tea, oak and honey attributes. The treatment consisting of enzyme followed by acid hydrolysis produced an artefact, apparently due to degradation of the added enzyme. Aroma attributes that characterise Chardonnay and Semillon wines were also aromas perceived in the hydrolysed precursor samples, indicating that grape precursors on hydrolysis contribute to and enhance these key aromas in the wines.
The volatile components of a Merlot and a Cabernet Sauvignon juice, as well as the volatile compounds released by acid- or glycosidase enzyme hydrolysis of C18 reverse phase isolates of the juices, have been analysed. The categories of constituents (i.e. monoterpenes, benzenoid compounds, norisoprenoids, aliphatic and miscellaneous compounds) and the components observed within these categories were broadly similar to those previously reported for other varieties. The potent flavour compound, damascenone, was a major component of the acid hydrolysates of both juice samples. The damascenone precursor trans-megastigma-6,7-diene-3,5,9-triol was identified as a hydrolysis product of grape-derived C18 reverse phase isolates for the first time.
Vinylphenols (4-vinylphenol and 4-vinylguaiacol) are natural constituents of wine and can play a role in wine aroma. However, only white wines contain important quantities of these volatile substances which, beyond a certain concentration (limit threshold = 725 μg litre−1 of 4-vinylguaiacol+4-vinylphenol (1:1)), can be responsible for a depreciating ‘phenolic’ or ‘pharmaceutic’ characteristic, Saccharomyces cerevisiae possesses a type-(E) enzymic activity, substituted cinnamate carboxy-lyase (SCD), which is capable of transforming, by non-oxidative decarboxylation, the phenolic acids in the must, (E) p-coumaric and (E) ferulic acids, into corresponding vinylphenols. This endocellular activity is constitutive, it is only expressed during alcoholic fermentation and with a variable intensity depending on the yeast strain. Furthermore, the enzyme is rapidly inhibited by catechic tannins, which explains why, in comparison with white wines, red and rosé wines contain low levels of vinylphenols despite having more precursors. A yeast strain with a weak SCD activity has been selected and its use in vinification should eliminate the appearance of the phenolic taint in white wines coming from grapes rich in decarboxylable hydroxycinnamic acids.
The exocellular β-glucosidases of Candida molischiana and Candida wickerhamii are able to hydrolyse geranyl, neryl, citronellyl, linalyl and α-terpinyl-β-D-glucopyranosides. The nature of the aglycone residue greatly affects the rate of hydrolysis. Glucosides with a tertiary alcohol as aglycone residue are more slowly hydrolysed than those with a primary alcohol. The β-glucosidase from C molischiana is also able to hydrolse α-L-arabinofuranosides. This results in the release of monoterpenols from a glycoside extract from grape juice.
Twenty-six strains of yeasts, belonging to the genera Candida, Debaryomyces, Hanseniaspora, Hansenula, Kloeckera, Metschnikowia, Pichia, Saccharomyces and Torulaspora previously isolated from wines, were screened for the production of extracellular pectinases, amylases, lipases, proteases and β-glucosidases. Some strains of Candida species and Hanseniaspora uvarum/Kloeckera apiculata produced extracellular proteolytic or lipolytic activities. Most yeasts exhibited β-glucosidase activity, but particularly high activity was observed in strains of Pichia anomala/Candida pelliculosa (formerly Hansenula anomala) and Hanseniaspora uvarum/Kloeckera apiculata. The potential impact of these enzymes on wine quality is discussed.
The use of yeasts other than Saccharomyces cerevisiae to produce wines with novel aroma and flavour profiles is gaining increased attention. The present study is concerned with the sensory impact on wine of fermentation with two selected Saccharomyces bayanus strains. The S. bayanus strains AWRI 1176 and AWRI 1375 were compared to S. cerevisiae strain AWRI 838 for their ability to affect the aroma profile and chemical composition of Chardonnay wine. Wines that were made with the S. bayanus strains contained more glycerol, succinic acid, acetaldehyde and SO2 than reference wines made with the S. cerevisiae wine yeast, but less acetic acid, malic acid and ethyl acetate. There were significant differences in the aroma profile of wines made with each yeast, as quantified by formal sensory descriptive analysis. Wines made with S. cerevisiae AWRI 838 were rated highly in the attributes ‘estery’, ‘pineapple’, ‘peach’ and ‘citrus’. Wines made with S. bayanus AWRI 1176 were rated lower than AWRI 838 in each of these attributes, but higher in the attributes ‘cooked orange peel’, ‘yeasty’, ‘nutty’ and ‘aldehyde’. The aroma profile of wine made using AWRI 1375 was different from that of wine made with the other yeasts, showing intermediate scores for the ‘estery’, ‘citrus’, ‘nutty’ and ‘aldehyde’ attributes, and no significant difference from the AWRI 838 strain in the attributes ‘pineapple’ and ‘peach’. These results demonstrate that, in addition to producing wine which has a different chemical composition, S. bayanus strains can produce a different sensory profile in wine when compared to a widely used S. cerevisiae wine yeast.
(R)-(+)-citronellol, a useful C10 chiral synthon for natural terpenoid products, can be obtained in enantiomerically pure form and satisfactory yield by yeast reduction of geraniol.
Using a model system, the activities of α-L-arabinofuranosidase, β-glucosidase, and α-L-rhamonopyranosidase were determined
in 32 strains of yeasts belonging to the genera Aureobasidium, Candida, Cryptococcus, Hanseniaspora, Hansenula, Kloeckera, Metschnikowia, Pichia, Saccharomyces, Torulaspora and Brettanomyces (10 strains); and seven strains of the bacterium Leuconostoc oenos. Only one Saccharomyces strain exhibited β-glucosidase activity, but several non-Saccharomyces yeast species showed activity of this enzyme. Aureobasidium pullulans hydrolyzed α-L-arabinofuranoside, β-glucoside, and α-L-rhamnopyranoside. Eight Brettanomyces strains had β-glucosidase activity. Location of enzyme activity was determined for those species with enzymatic activity.
The majority of β-glucosidase activity was located in the whole cell fraction, with smaller amounts found in permeabilized
cells and released into the growth medium. Aureobasidium pullulans hydrolyzed glycosides found in grapes.
The purpose of this study was to verify whether both wine yeasts belonging to different species (Metschnikowia pulcherrima (2), Debaryomyces hansenii, Kluyveromyces thermotolerans, Saccharomyces cerevisiae (3), Hanseniaspora uvarum, Pichia kluyveri) and a non-wine yeast (Candida molischiana), were able to hydrolyse the terpenoids, norisoprenoids and benzenoids glycosides occurring in Muscat must and transform the produced aglycons. The results obtained confirmed the role played by yeasts in releasing volatile compounds from non-volatile precursors. Among wine yeasts, Hanseniaspora uvarum was able to hydrolyse both glycoconjugated forms of pyranic and furanic oxides of linalool.
Following a brief look at the structure and occurrence of glycosidic flavour precursors in plants and fruits, attention is given to mechanisms of enzymatic hydrolysis, the properties of relevant glycosidases, as well as endogenous and exogenous glycosidases affecting flavour release in plants, in fruit juice processing and in winemaking. The constraints for technological applications and future prospects are discussed.
The mechanism of action of α-l-arabinofuranosidase, α-l-rhamnopyranosidase, and β-d-glucopyranosidase on p-nitrophenyl and grape monoterpenyl disaccharide-glycosides has been studied. First, the (1→6) linkage is cleaved by either α-l-arabinofuranosidase or α-l-rhamnosidase, and arabinose, rhamnose, and the corresponding monoterpenyl β-d-glucosides are released. Subsequently, liberation of monoterpenol takes place after action of β-d-glucosidase. The possible use of these glycosidases for the enhancement of the aroma of grape juice and derived beverages is emphasised.
A method of extraction and determination of free and glycosidically bound terpenols and of benzyl and 2-phenylethyl alcohols is suggested. The extraction was carried out by adsorbing these compounds on a non-ionic resin, Amberlite XAD-2, and then elution with various selective solvents. Free forms were directly determined by gas chromatography; glycosidically bound forms were first enzymatically hydrolysed to release aglycones. This method was applied to a number of mature grape varieties. The levels of glycosidically bound terpenols and aromatic alcohols were always high, usually much higher than the free forms. The varieties can be classified in two groups: those rich in free and bounds forms which give aromatic wines (Muscat varieties and Gewürztraminer), and those which contain small amounts of these compounds and which give more neutral wines.
Glycoconjugated aroma precursors from neutral grape varieties were fractionated on 5 g C18 RP cartridge. Each of the seven fractions collected was divided in three parts: first part was hydrolysed with Pectinol in order to determine total aromatic heterosides, while the second part was treated with an active strain of the yeast Saccharomyces cerevisiae UCLM 325 and the third part with acetonic powder of the same yeast strain. The studied strain proved effective in the hydrolysis of the heterosides of nerol and geraniol, cis-8-hydroxy-linalool, 8-hydroxy-dihydro-linalool, some benzenoids and some norisoprenoids derivatives such as vomifoliol and 3-oxo-α-ionol. Only whole cells are able to convert geraniol to citronellol.
Synthetic monoterpene and aromatic beta-D-glucopyranosides, beta-rutinosides and 6-O-(alpha-L-arabinofuranosyl)-beta-D-glucopyranosides and their corresponding alcohols, diluted in a synthetic solution imitating wine, were isolated and separated by selective retention on Amberlite XAD-2. The corresponding recoveries and the conditions for the direct determination of these glycosides by gas chromatography and gas chromatography-mass spectrometry after derivatization were determined. Trifluoroacetylation gave the best results but trimethylsilylation provided complementary results. The separation of some diastereoisomeric monoterpene glycosides was also examined.
Free and glycosidically bound terpenes of five Vitis vinifera grape cultivars (muscat of Alexandria, muscat of Frontignan, muscat of Hamburg, muscat Ottonel and Gewürztraminer) were investigated. The free and bound fractions were separated by selective retention on Amberlite XAD-2 resin. The glycosidic fractions were analysed by gas chromatography and gas chromatography-mass spectrometry using either enzymic hydrolysis and subsequent analysis of the released aglycones or trimethylsilyl (TMS) and trifluoroacetyl derivatives. The known monoterpenyl, benzyl and 2-phenylethyl beta-D-glucopyranosides, beta-rutinosides, 6-O-alpha-L-arabinofuranosyl-beta-D-glucopyranosides and 6-O-beta-D-apiofuranosyl-beta-D-glucopyranosides were determined. A number of other glycosides were detected and the structures of some of them, mainly apiosylglucosides and glucosides with aglycones in higher oxidation state than linalol, were tentatively identified using the mass spectra of their TMS and TFA derivatives and the results obtained from the analysis of their aglycones.
AMP deaminase, 5'-nucleotidase and adenosine deaminase have been estimated in skeletal muscle and myocardial tissue in normal rats and in rats subjected to experimental myocardial infarction or hypothermia. A difference in the enzyme distribution was found between the right and left ventricles in the normal rat. A decrease in the activity of 5'-nucleotidase and an increase in the activity of adenosine deaminase were observed in infarcted myocardial tissue. The activity of all 3 enzymes was found to be depressed in the myocardium in rats subjected to hypothermia. These results are discussed in relation to adenosine production and its beneficial effects.
The glycosides in mono-, di- and trihydroxylated terpene and norisoprenoid alcohols and also those in the related shikimate pathway have been isolated on C18 reversed-phase cartridges and then fractionated into classes of different polarity at increasing percentages of methanol. The benzyl alcohol glycosides are the most polar, while those of terpene monohydroxylated alcohols and geranic acid are the least polar. The terpene diols, linalool furanoid and pyranoid oxides and also norisoprenoid precursors show intermediate polarity and separate into well defined fractions according to their polarity.
Twenty-six synthetic glycosides constituting aglycons of the main tea aroma compounds ((Z)-3-hexenol, benzyl alcohol, 2-phenylethanol, methyl salicylate, geraniol, linalool, and four isomers of linalool oxides) were synthesized in our laboratory as authentic compounds. Those compounds were used to carry out a direct qualitative and quantitative determination of the glycosides as aroma precursors in different tea cultivars by capillary gas chromatographic-mass spectrometric (GC-MS) analyses after trifluoroacetyl conversion of the tea glycosidic fractions. Eleven beta-D-glucopyranosides, 10 beta-primeverosides (6-O-beta-D-xylopyranosyl-beta-D-glucopyranoside) with aglycons as the above alcohols, and geranyl beta-vicianoside (6-O-alpha-L-arabinopyranosyl-beta-D-glucopyranoside) were identified (tentatively identified in the case of methyl salicylate beta-primeveroside) in fresh tea leaves and quantified on the basis of calibration curves that had been established by using the synthetic compounds. Primeverosides were more abundant than glucosides in each cultivar we investigated for making green tea, oolong tea, and black tea. Separation of the diastereoisomers of linalool and four isomers of linalool oxides by GC analyses is also discussed.
Glycoconjugates from Muscat of Alexandria and Shiraz leaves and grape berries were isolated by adsorption on Amberlite XAD-2 resin, and enzymatically released aglycons were analyzed by GC-FID and GC-MS. About 120 aglycons were fully or tentatively identified. Compositional differences were observed between leaves and berries of the two varieties in five aglycon chemical groups: C6 alcohols, aliphatic alcohols, monoterpenes, shikimates, and C(13)-norisoprenoids, which were much more abundant in the leaves than in the berries. The differences observed for C(13)-norisoprenoids were in agreement with their hypothetical independent biosynthesis in leaves and berries. Thus, 3-hydroxy-beta-damascone, an important norisoprenoid aglycon of grape berries, was not detected in leaves, whereas its oxidized derivative, 3-oxo-alpha-damascone, was absent in berries. Compositional differences were also observed between Muscat and Shiraz leaves. 3-Oxo-alpha-ionol was not detected in Shiraz leaves, and its retro derivatives were less abundant than in Muscat of Alexandria leaves. Conversely, in Shiraz leaves the levels of 7,8-dihydroionone derivatives, such as megastigman-3,9-diol and 3-oxo-7,8-dihydro-alpha-ionol, were higher than in Muscat of Alexandria leaves.
Experiments were designed to demonstrate the actual contribution of yeast in the formation of the primary aroma during the vinification of neutral grapes. Ruché was chosen as the model wine to study because of its unique fragrance. A yeast strain specific for Ruché was selected using a new and rapid isolation method for red wines. The results of this study can be summarized as follows: Skins from nonaromatic white or red grapes apparently contain most of the primary aroma compounds that are revealed in the must only after contact with yeast cells under defined conditions. Similar results were obtained with the pulp and seeds fractions; however, the olfactory notes, although well characterized, differed from those obtained with skins alone. Clarification, filtration, and centrifugation of the pulp and seed fractions or sonification of the skins produce different and well-characterized olfaction notes during the contact with yeast. The primary aroma of nonaromatic white and red grapes contained in the skins can be revealed within 24-48 h of yeast contact in a synthetic nutrient medium (SNM). The primary aroma precursors extracted from the skins with methanol, water-saturated butanol, or aqueous buffer at pH 3.2, concentrated and eluted from a C18 resin column, can be transformed to the free form wine aroma markers within 6 h of contact with yeast cells in SNM. By contrast, prolonged maceration of the skins in aqueous alcoholic buffer at pH 3.2 or 1.1, at 50 or 70 degrees C did not release primary odors typical of wine. The individual primary aroma compounds, identified by GC-MS analysis in Ruché wine samples or in Ruché skin-yeast-SNM samples, could not explain the complexity of the typical Ruché wine odor. Only odors common to many wine varieties were identified by GC-olfactometry analysis.
The volatile monoterpenic and norisoprenoidic compounds released by glycosidase enzyme hydrolysis of C18 reversed-phase isolates from the juice of Vitis vinifera L. cv. Melon B. have been qualitatively and quantitatively determined using GC-MS and GC-FID. The components analyzed were broadly similar to those previously reported for other varieties but the level of bound p-menth-1-en-7,8-diol was higher in this cultivar. Then the monoterpenic and norisoprenoidic volatiles released from the same glycosidic extracts under mild acid conditions, mimicking wine aging conditions, have been analyzed using GC-Olfactometry and GC-MS. The most odorous compounds detected were p-cymene, terpinen-4-ol, cis- and trans-vitispiranes, 1,6,6-trimethyl-1,2-dihydronaphtalene (TDN), beta-damascenone and riesling acetal. To assess their potential levels in corresponding wines after ageing, most of these odorants were generated by harsh acid hydrolysis from the precursors extracts and quantitatively determined using SPME and GC-MS/MS. For the development and application of this analysis, the odorants not commercialy available were synthesized. The total amounts of norisoprenoidic odorants generated by acid hydrolysis of the glycosidic extracts were shown to be proportional to the total amounts of these precursors.