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The effect of various wine bottle closures and fining agents on flavour and aroma compounds in wine
... This chapter also describes a number of analytical methods, which were developed by others, that were used to measure the study wines for various volatile aroma compounds including a range of grape-and oak-derived compounds [171][172][173], 4-vinylguaiacol and 4-vinylphenol [174], methionol (unpublished method), low molecular weight sulfur compounds and (E)-1-(2,3,6-trimethylphenyl)buta-1,3-diene (TPB) [39,40]. ...
... Various analytical methods were available for use by the author for the measurement of volatile compounds that had been targeted for analysis in the study wines. An analytical method, involved SIDA, liquid/liquid extraction and GC-MS, for the measurement of a number of monoterpenes, norisoprenoids and oak-derived compounds in white wine (13 in total) had previously been developed [171][172][173] (details given in Section 2.4.1 and Section 2.4.4). The analysis of 4-vinylguaiacol and 4-vinylphenol was conducted by the author using existing methods [174] and involved SIDA, SPME and GC-MS (details given in Section 2.4.1 ...
... This contrasts with previous findings (Miller, Amon, Gilson, & Simpson, 1985) that demonstrated reduced concentration of aroma compounds after bentonite addition to juice, must, or wine. Moreover, Pollnitz, Capone, Caldersmith, and Sefton (2003) confirmed that aroma compounds could be absorbed by bentonite, as did Cabaroglu, Razungles, Baumes, and Gunata (2003), although the later study found no sensory effect of bentonite fining on Muscat Ottonel or Gewurztraminer wines. This is probably because the higher the aromatic intensity of a wine, i.e., Sauvignon blanc, Gewurztraminer, the lower the sensory impact is. ...
Both organic and inorganic fining agents (bentonite) are commonly used to clarify and stabilize white wines, thus preventing haze formation (i.e., protein haze) in wines after bottling. Fining involves the formation of a floccular precipitate in wine, which will absorb or entrain the natural haze-forming constituents and colloidal particles while settling. The fining process must also be reasonably rapid, and the loss of saleable product in the sediment or lees should be minimal. Recently, issues related to the allergenic potential of the proteinaceous fining agents used in winemaking were identified and a demand for nonallergenic products has increased. Finally, the fining process should not have any undesirable effects, like the removal of desired flavor or addition of undesired flavor components. It is thus our intention here to review the chemistry of fining and present some results of recent investigations.
... This contrasts with previous findings (Miller, Amon, Gilson, & Simpson, 1985) that demonstrated reduced concentration of aroma compounds after bentonite addition to juice, must, or wine. Moreover, Pollnitz, Capone, Caldersmith, and Sefton (2003) confirmed that aroma compounds could be absorbed by bentonite, as did Cabaroglu, Razungles, Baumes, and Gunata (2003), although the later study found no sensory effect of bentonite fining on Muscat Ottonel or Gewurztraminer wines. This is probably because the higher the aromatic intensity of a wine, i.e., Sauvignon blanc, Gewurztraminer, the lower the sensory impact is. ...
... This contrasts with previous findings of Miller et al. (1985) that demonstrated reduced concentration of aroma compounds after bentonite addition to juice, must or wine. More recently Pollnitz et al. (2003) elegantly confirmed that aroma compounds can be absorbed by bentonite, as did Cabaroglu et al. (2003), although the later study found no sensory effect of bentonite fining of V. vinifera cv. Muscat Ottonel or Gewürztraminer wine. ...
Slow denaturation of wine proteins is thought to lead to protein aggregation, flocculation into a hazy suspension and formation of precipitates. The majority of wine proteins responsible for haze are grape-derived, have low isoelectric points and molecular weight. They are grape pathogenesis-related (PR) proteins that are expressed throughout the ripening period post véraison, and are highly resistant to low pH and enzymatic or non-enzymatic proteolysis. Protein levels in un-fined white wine differ by variety and range up to 300 mg/L. Infection with some common grapevine pathogens or skin contact, such as occurs during transport of mechanically harvested fruit, results in enhanced concentrations of some PR proteins in juice and wine. Oenological control of protein instability is achieved through adsorption of wine proteins onto bentonite. The adsorption of proteins onto bentonite occurs within several minutes, suggesting that a continuous contacting process could be developed. The addition of proteolytic enzyme during short term heat exposure, to induce PR protein denaturation, showed promise as an alternative to bentonite fining. The addition of haze-protective factors, yeast mannoproteins, to wines results in decreased particle size of haze, probably by competition with wine proteins for other non-proteinaceous wine components required for the formation of large insoluble aggregations of protein. Other wine components likely to influence haze formation are ethanol concentration, pH, metal ions and phenolic compounds.
... Oak flavour compounds (cis-oak lactone, transoak lactone, guaiacol, 4-methyl guaiacol and vanillin) were determined using headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GCMS), with polydeuterated internal standards for stable isotope dilution analysis (SIDA) as described previously (Pollnitz et al. 2004). Grape-derived volatile compounds (naphthalene, linalool , a-terpineol, nerol, b-damascenone and geraniol) were analysed using HS-SPME-GCMS with SIDA as described elsewhere (Pedersen et al. 2003, Pollnitz et al. 2003 ). Yeast volatile sulphur compounds (hydrogen sulphide , methanethiol, dimethyl sulphide (DMS), carbon disulphide (CS2), dimethyl disulphide and diethyl disulphide ) were determined by using headspace cool-oncolumn gas chromatography coupled with an atomic emission detector, with ethyl methyl sulphide and propyl thioacetate as internal standards (T.E. ...
Background and Aims: Winemakers are constantly searching for new techniques to modulate wine style. Exploiting indigenous yeasts present in grape must is re-emerging as a commercial option in New World wine regions. Wines made with indigenous or ‘wild’ yeasts are perceived to be more complex by showing a greater diversity of flavours; however, the chemical basis for the flavour characteristics is not yet defined. In order to evaluate techniques for making wine with the ‘wild yeast fermentation’ character more reliably, it is necessary to define the salient chemical characteristics of such wines.Methods and Results: Pairs of Chardonnay wines were prepared from the same must and subjected to similar fermentation conditions in the wineries of origin, except for the mode of inoculation. Reference wines were made by inoculation with a Saccharomyces cerevisiae starter culture, whereas companion wines were allowed to undergo fermentation with the indigenous microflora. Of all wine chemicals analysed, only yeast-derived volatile fermentation products showed significant differences between the yeast treatments.Conclusions: Inoculated wines were associated with the esters ethyl hexanoate and 3-methylbutyl acetate and formed a clear cluster by principal component analysis. By comparison with inoculated wines, ‘wild’ yeast fermented wines showed high variability in volatile compounds that contribute to wine aroma, with higher concentrations of 2-methylpropanol, 2-methylbutanoic acid, ethyl 2-methylpropanoate, ethyl decanoate and ethyl dodecanoate potentially being sensorially important.Significance of the Study: This study shows that yeast-derived volatile fermentation products are a key difference between inoculated and uninoculated ferments and provides a chemical basis for the ‘wild yeast fermentation’ character.
... The effects of bentonite treatment on the sensorial characteristics of wines are not clear. Some studies affirm that the aromatic profile of bentonite-fined wines is not modified (Leske et al. 1995, Pocock et al. 2003, while others show that its use can decrease the concentration of aroma compounds (Miller et al. 1985, Pollnitz et al. 2003. However, practitioners generally believe that bentonite fining is detrimental for wine aroma and flavour (Waters et al. 2005), and so alternatives are sought. ...
Backgrounds and Aims: Bentonite is commonly added to white wines to remove the grape proteins responsible for haze formation. Despite being effective, this technique has drawbacks; thus, new solutions are desirable. The ability of carrageenan and pectin to remove heat-unstable grape proteins, and the impact that such addition has on the physicochemical and sensorial profile of a wine were assessed.
Methods and Results: Carrageenan and pectin were added separately or in combination to a Chardonnay juice prior to fermentation. Both adsorbents removed proteins (up to 75%), thus increasing wine protein stability. Carrageenan was more effective than pectin at increasing wine protein stability.
Conclusions: Pectin and carrageenan removed protein and partially stabilized the samples of the wine.
Significance of the Study: Pre-fermentation addition of pectin or carrageenan may provide the wine industry with an alternative protein stabilization procedure.
Both organic and inorganic fining agents (bentonite) are commonly used to clarify and stabilize white wines, thus avoiding the appearance of haze in the bottle. Fining involves the formation of a floccular precipitate in wine which will absorb or entrain the natural haze-forming constituents and colloidal particles while settling. The fining process must also be reasonably rapid, and the loss of saleable product in the sediment or lees should be minimal. Finally, the fining process should not have any undesirable effects, like removal of desired flavour or addition of undesired flavour components. It is thus our intention here to review the chemistry of fining and present some results of recent investigations.
Grape and wine proteins have been of interest to winemakers for many years. This interest is primarily due to the ability of these proteins to aggregate together in finished white wines and form unattractive hazes and sediments. Proteins are significant in wine because they are a nuisance! Endogenous wine proteins, of course, also have other roles in wine and have been examined for their impact on the aroma and taste of wines (Jones et al. 2008; Peng et al. 1997), on bubble persistence and bead in sparkling wines (Girbau-Sola et al. 2002; Liger-Belair 2005; Senee et al. 1999), on lacquer-like bottle deposit in red wines (Peng et al. 1996a, b;Waters et al. 1994) and as allergens in rare cases of grape and wine allergy (Pastorello et al. 2003; Sbornik et al. 2007; Schad et al. 2005; Vassilopoulou et al. 2007). This chapter will focus on the role of endogenous wine proteins in white wine haze formation. It will not cover the other roles of protein listed above nor will it describe the roles and consequences of food proteins such as casein, egg white and isinglass, used in wine processing. Published scientific studies of these proteins and of protein haze in wine began in earnest in the late 1950s and early 1960s with work by J. Koch in Geisenheim (Koch and Sajak 1959), H.W Berg, at the University of California, Davis (Bayly and Berg 1967; Berg and Akiyoshi 1961; Moretti and Berg 1965) and B. Rankine at the AustralianWine Research Institute in Adelaide (Rankine 1962).
Field tests to evaluate in-line dosing with bentonite followed by centrifugation as an alternative to batch fining for protein haze control in white wine or juice were undertaken. The tests were performed at a commercial winery with a Sultana wine and Gordo (Muscat of Alexandria) juice and using two types of bentonite: Vitiben and SIHA-Active-Bentonite G. Fining performance was monitored by heat testing and quantification of heat unstable protein by HPLC. Heat test turbidity and heat unstable protein concentration decreased to stable values between 30 s and 2 min after bentonite injection. Sensory evaluation of Sultana wine fined with Vitiben by balanced reference duo-trio difference tests detected no difference between untreated, in-line dosed, and batch fined wine. Furthermore the volume of wine or juice occluded in lees can be substantially reduced by centrifugal compaction. However, incomplete separation of bentonite from wine or juice during centrifugation produced a carryover of 30% of the added bentonite into the clarified wine. This carryover problem may be mitigated, inter alia, by reducing operating flowrate through the centrifuge or using multiple centrifugation steps (in parallel or series). Therefore, inline dosing followed by centrifugation provides a rapid processing method for protein haze reduction in wine or juice with a decreased volume of lees. It can reduce significant value losses presently arising in the wine industry from batch fining and the resulting quality downgrades that occur in wine recovered from bentonite lees by rotary drum vacuum filtration.
The influence of interactions among wine proteins, wine polysaccharides, volatile compounds, glycerol and ethanol on the sensory properties of a model wine was assessed. Variation in the concentration of volatiles and ethanol had the largest effects on aroma and mouthfeel attributes, respectively. Several aroma attributes were significantly affected by protein, alcohol and glycerol concentration, but most of the interactions affecting perceived aroma were strongest when volatile concentration was low. Polysaccharides slightly suppressed the intensity of overall aroma. Overall flavour intensity was positively influenced by glycerol. The perceived viscosity was increased in the presence of glycerol and to a lesser extent, polysaccharides. A higher alcohol level enhanced the ‘unpleasant’ textural characteristics of hotness, roughness and bitterness while glycerol suppressed them. In the absence of polysaccharides, high ethanol levels were also associated with an undesirable metallic character. None of the factors under study significantly affected the sweetness of the model wine.
The effect of red wine malolactic fermentation on the fate of seven fungicides (carbendazim, chlorothalonil, fenarimol, metalaxyl, oxadixyl, procymidone, and triadimenol) and three insecticides (carbaryl, chlorpyrifos, and dicofol) was investigated. After malolactic fermentation using Oenococcus oeni, which simulated common Australian enological conditions, the concentrations of the active compounds chlorpyrifos and dicofol were the most significantly reduced, whereas the concentrations of chlorothalonil and procymidone diminished only slightly. The effect of these pesticides on the activity of the bacteria was also studied. Dicofol had a major inhibitory effect on the catabolism of malic acid, whereas chlorothalonil, chlorpyrifos, and fenarimol had only a minor effect.
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