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Studying the Non-thermal effects of microwave on amino acids in sterilized rainbow trout (Oncorhynchus mykiss) fillets using a Double Side Approximating Method
A pulsed electric field (PEF: 2.0 kV/cm) was applied before vacuum microwave drying (VMD: 120 W, 120/260 W, and 260 W at 40 kPa) on Chilean abalone mollusks. PEF and VMD effects on process features (drying kinetics, modeling, and sustainability) and product quality (texture, structure, and digestibility) were measured. The PEF application increased moisture diffusivity by up to 27% in the combined PEF+VMD process. According to the statistical analysis applied to all mathematical models, the Logarithmic model was best fitted to VMD experimental values. In terms of energy consumption, applying PEF+VMD reduced energy consumption by up to 33% of the 120W and 120/260W non-PEF samples. The best values for the rehydration index were obtained with the 120/260W (45%) and PEF+120/260W (61%) treatments. In addition, these samples had the best texture parameters. The PEF+120/260W treatment showed the highest degree of hydrolysis (11%) for the calculated protein efficiency. Finally, using PEF as a pretreatment in a VMD process can be cost-effective for scale replication due to its time efficiency and product quality to Chilean abalone samples.
Graphical Abstract
The objective of this study was to explore the thermal degradation characteristics of amino acids in rainbow trout (Oncorhynchus mykiss) fillets processed by microwave and different traditional high temperature short time (HTST) sterilization. A custom-built thermal processing system was used to conduct the HTST processing with different parameters including heating rate (5.52–19.56 °C/min), maximum heating temperature (123, 133 °C) and thermal processing level (F0 = 3.0, 6.0 min). Microwave processing was conducted by a single-mode pilot microwave processing system. Results showed that rainbow trout fillets in processing with higher heating rates retained obviously more amino acids, which verified the great potential of HTST processing in the quality improvement of solid food products. Furthermore, heating rate had no effect on the thermal sensitivity of each amino acid. Raising the maximum heating temperature led to higher thermal degradation of amino acids, which demonstrated that extra high temperature might impair the quality improvement of traditional HTST processing. Compared with traditional HTST processed samples, the retention of amino acids in fish fillets processed by microwave processing was higher. Furthermore, the degradation rate of each amino acid in microwave processed samples was different with traditional HTST processed samples. These results showed that microwave processing could retain higher product quality and may provide non-thermal effects due to alternative electromagnetic fields.
The quality changes of duck meat during thermal sterilization using microwave, stepwise retort and general retort heating were evaluated. Results showed that compared with stepwise retort and general retort, duck meat subjected to microwave showed significantly higher gumminess, chewiness, cohesiveness and resilience as well as glutamic acid, lysine and total amino acids. Low-field NMR revealed that the relative content of immobilized water after microwave and stepwise retort treatment was significantly higher than that after general retort treatment. The relative content of 1-octen-3-ol with characteristic mushroom aroma was significantly higher with microwave and stepwise retort heating than with general retort heating, while 2-pentyl-furan with poor taste was only detected with general retort heating. The muscle bundles subjected to microwave were neatly arranged, similar to those with no thermal sterilization. Overall, the meat quality after three thermal sterilization treatment was microwave > stepwise retort > general retort.
In this paper, we study the rigidity theorem of closed minimally immersed Legendrian submanifolds in the unit sphere. Utilizing the maximum principle, we obtain a new characterization of the Calabi torus in the unit sphere which is the minimal Calabi product Legendrian immersion of a point and the totally geodesic Legendrian sphere. We also establish an optimal Simons’ type integral inequality in terms of the second fundamental form of three-dimensional closed minimal Legendrian submanifolds in the unit sphere. Our optimal rigidity results for minimal Legendrian submanifolds in the unit sphere are new and also can be applied to minimal Lagrangian submanifolds in the complex projective space.
Key message
Sweet cherry tree branches have important food and medicinal value. The ultrasound and microwave-assisted extraction method is more efficient with higher yield than conventional extraction methods (heat-reflux, Soxhlet, etc.).
Abstract
Plant byproducts are known as sources of natural bioactive compounds. The objective of this study was to rationally use sweet cherry tree branches (SCTB) discarded during pruning. Ultrasonication and microwaves are considered green techniques, and an ultrasound and microwave-assisted extraction (UMAE) method was established to obtain extracts from SCTB by response surface methodology. A mathematical model was established using the Box–Behnken design, and the effects of various factors and their interactions were analyzed as well. Taking the yield (w/w) as the objective, the optimal process conditions for UMAE of SCTB were 56 mL·g⁻¹ liquid–solid ratio, 34 min extraction time, and 40–50 mesh particle size. The yield of SCTB extracts was 5.02%, which was close to the theoretical prediction. The optimized extraction process can obtain a higher yield than that of conventional extraction methods. The chemical composition of the extracts was identified by HPLC–MS/MS, and 400 metabolites, including carboxylic acids and derivatives (29%), fatty acyls (19%), organooxygen compounds (15%), flavonoids (12%), benzene and substituted derivatives (12%), phenols (8%), and imidazopyrimidines (5%), were annotated and classified. L-arginine and mannitol were the main chemical components of the SCTB extracts, suggesting their potential uses in the food and medical industries.
Graphic abstract
In this study, the production of antihypertensive and antioxidant hydrolysates by microwave assisted enzymatic hydrolysis was optimized for the proteins extracted from the rice bran. The central composite design was used for optimization and the independent parameters were solid/liquid ratio, power, and time. Optimum protein extraction parameters were obtained as; 0.42 solid/liquid ratio, 100.68 W power, 100.68 s. During alcalase and pepsin hydrolysis, solid/liquid ratio and time were selected independent factors, the results of angiotensin-converting enzyme (ACE) inhibitory activity, degree of hydrolysis (DH), and DPPH radical scavenging activity were used as responses. Optimum hydrolysis parameters were determined. The DH, DPPH radical scavenging activity, ACE inhibitory activity, values were 40.60%, 36.26%, and 59.16% respectively. The rice bran protein hydrolysates was fractionated as < 1 kDa, 1–5 kDa, and 5–10 kDa by ultrafiltration. The highest ACE inhibition activity, DPPH, and OH radical scavenging activity and Trolox equivalent antioxidant activity values were respectively obtained for 5–10 kDa fraction as 76.66%, 13.25%, 5.03%, and 8.82 µg trolox/mg sample. The study may provide a new approach for obtaining biofunctional protein hydrolysates from rice bran emerging relatively high volumes as a by-product during paddy processing.
A comparative evaluation on the effect of carbon dioxide (CO2) on quality and shelf life of Atlantic salmon loins pasteurized with microwave and conventional technology was conducted. The experimental design allowed CO2 to enter the salmon muscle before (soluble gas stabilization [SGS] + vacuum) or after pasteurization (CO2 emitter + vacuum), whereas the control samples (vacuum only) were not presented for CO2. This setup resulted in six different groups; three heated with microwaves and three with conventional pasteurization. The core temperature of microwave samples was 58.8 ± 2.2 °C, whereas the surface temperature was equal to the oven temperature (62 °C) during conventional pasteurization and close to the core temperature during microwave pasteurization (57.6 ± 1.4 °C). Microwave‐heated samples showed higher microbial growth; decreased shelf life; and darker (lower L*‐value), more reddish (higher a*‐value), and yellowish (higher b*‐value) colors compared to conventional‐heated salmon. Lowest liquid loss (LL) was observed in salmon packaged with the CO2 emitter, whereas a SGS step prior to pasteurization did not affect the LL negatively as compared to samples packaged in vacuum only. Treatment with CO2, independent of the prestep using SGS or an emitter, resulted in increased shelf life. Protein denaturation, microbial growth, product color, product shelf life, and sensory properties of the salmon loin were significantly affected by the applied pasteurization method (microwave‐ or conventional pasteurization). However, the heat load was probably too high to detect differences resulting from the pretreatment using SGS or packaging with CO2 emitter.
Practical Application
Recent developments with increased time pressure from both work and past time activities have led to a tremendous increase in the demand for convenient, tasty ready‐to‐use food options. Furthermore, contemporary trends for consumption of fresh or lightly processed seafood stress the need to develop processing methods that allow a fulfillment of these demands, while still offering a reasonable shelf life. Carbon dioxide in combination with either microwave or conventional pasteurization is innovative processing technology that can meet consumer's demand of such products.
During heating, there are a lot of physical and chemical changes in milk components, which are mainly reflected in the changes of proteins. Calcium ions in milk react with proteins to precipitate or form gels, and the thermal stability of milk is affected by the type and content of calcium. In this study, different calcium-fortified milk systems were treated by rapid conventional heating (RCV) and microwave heating (MV) to evaluate the effects of forms and concentration of calcium in liquid milk on microwave absorption properties and thermal stability of milk. It was found that the concentration of calcium ions on microwave energy absorption is not a significant influence, while the forms affected the systems dramatically. The thermal stability of milk during MV is remarkably affected by the forms of calcium ions. When adding ionized calcium, the calcium-fortified milk systems had poor thermal stability and severe agglomeration of protein, while the addition of milk calcium had little effect and was almost free from protein coagulation. It could be speculated that the metal ions in the microwave field could create a strong vibration that could trigger protein agglomeration through the combination of the surrounding casein phosphorylates.
In this research biochemical, amino acid and fatty acid compositions of wild and cultured sea bass (Dicentrarchus labrax) were compared.Crude protein (CP), crude fat (CF) and moist contents were 19.13% and 18.0%; 8.90% and 10.30%; 68.37% and 68.83% for wild and cultured sea bass, respectively. Essential amino acid (EAA) were 6921±11 and 7360.5±266.5 mg/100g in wild and cultured sea bass, respectively and the differences between them were insignificant (P>0.05). Saturated fatty acid (ƩSFA) were 26.50±0.06% and 25.11±0.01% in wild and cultured sea bass, respectively, and the differences between them was significant (P<0.05). Mono unsaturated fatty acids (ƩMUFA) were 27.55±0.22% and 30.14±0.02% andpoly unsaturated fatty acids (ƩPUFA) were 35.06±0.02% and 33.82±0.12% in wild and cultured sea bass respectively and the results between them were found insignificant (P>0.05).n3/n6rates were 2.02±0.01 and 1.02±0.06 inwild and cultured sea bass, respectively (P<0.05).It was found that C18:2n6c linoleic acid, C18:3n3a-linolenic acid and C22:1n9 erucic acid values in cultured sea bass and C20:5n3 EPA and C22:6n3 DHA in wild sea bass values were high.
Microwave is an effective means to deliver energy to food through polymeric package materials, offering potential for developing short-time in-package sterilization and pasteurization processes. The complex physics related to microwave propagation and microwave heating require special attention to the design of process systems and development of thermal processes in compliance with regulatory requirements for food safety. This article describes the basic microwave properties relevant to heating uniformity and system design, and provides a historical overview on the development of microwave-assisted thermal sterilization (MATS) and pasteurization systems in research laboratories and used in food plants. It presents recent activities on the development of 915 MHz single-mode MATS technology, the procedures leading to regulatory acceptance, and sensory results of the processed products. The article discusses needs for further efforts to bridge remaining knowledge gaps and facilitate transfer of academic research to industrial implementation.
© 2015 Institute of Food Technologists®
The proximal point algorithm (PPA) for the convex minimization problem min x member of H$/f(x), where f:H → R union {∞} is a proper, lower semicontinuous (lsc) function in a Hilbert space H is considered. Under this minimal assumption on f, it is proved that the PPA, with positive parameters {λ k} k=1∞, converges in general if and only if σ n = Σ k=1n λ k → ∞. Global convergence rate estimates for the residual f$x n) - f(u), where x n is the nth iterate of the PPA and u member of H is arbitrary are given. An open question of Rockafellar is settled by giving an example of a PPA for which x n converges weakly but not strongly to a minimizer of f.
The present study was conducted to determine fatty acid profile, amino acid and mineral content of rainbow trout from Indian Himalayan region. The crude protein, crude fat and ash content were 19.44, 5.18 and 1.37% respectively. Protein had a well-balanced amino acid composition, with higher amounts of proline. The highest amino acid score was observed for tryptophan followed by isoleucine. Total monounsaturated fatty acids were high followed by saturated fatty acids and polyunsaturated fatty acids. Oleic acid was dominant, followed by palmitic acid and linoleic acid. Among the n-3 PUFAs, DHA was the most dominant followed by linolenic acid. The ratio of n-3/n-6 PUFA was 0.77. Among the minerals, K was high followed by Ca, Na, Fe, Zn, Se and Mn. From the present study, it can be concluded that rainbow trout has a rich amount of quality protein with well-balanced essential amino acids, PUFAs and minerals. © 2015, Agricultural Research Communication Centre. All rights reserved.
The objective of this current study was to analyze the biochemical compositions of three Malaysian Channa spp. fish. The proximate analysis revealed that the protein content of Channa lucius, Channa micropeltes and Channa striatus was 19.9%, 22.1%, 23.0% (% of dry weight), respectively. The total lipid content was generally high, ranging from 5.7% to 11.9% and crude ash ranged from 1.0% to 1.8%. The major amino acids were glutamic acid, aspartic acid and lysine, ranging from 9.7% to 21.7%, and the most abundant fatty acid in Channa spp. was C16:0, ranging from 25.6% to 30.4%. The other major fatty acids detected were C22:6, C18:1 and C18:0. The level of arachidonic acid (C20:4) was unusually high in C. striatus (19.02%). The levels of DHA in these fish would also explain the use of Channa spp., especially C. striatus, which has been used for centuries for reducing pain, inflammation and promote wound healing in Malaysia.
Amino acids (AA) were traditionally classified as nutritionally essential or nonessential for animals and humans based on nitrogen balance or growth. A key element of this classification is that all nonessential AA (NEAA) were assumed to be synthesized adequately in the body as substrates to meet the needs for protein synthesis. Unfortunately, regulatory roles for AA in nutrition and metabolism have long been ignored. Such conceptual limitations were not recognized until recent seminal findings that dietary glutamine is necessary for intestinal mucosal integrity and dietary arginine is required for maximum neonatal growth and embryonic survival. Some of the traditionally classified NEAA (e.g. glutamine, glutamate, and arginine) play important roles in regulating gene expression, cell signaling, antioxidative responses, and immunity. Additionally, glutamate, glutamine, and aspartate are major metabolic fuels for the small intestine and they, along with glycine, regulate neurological function. Among essential AA (EAA), much emphasis has been placed on leucine (which activates mammalian target of rapamycin to stimulate protein synthesis and inhibit proteolysis) and tryptophan (which modulates neurological and immunological functions through multiple metabolites, including serotonin and melatonin). A growing body of literature leads to a new concept of functional AA, which are defined as those AA that regulate key metabolic pathways to improve health, survival, growth, development, lactation, and reproduction of organisms. Both NEAA and EAA should be considered in the classic "ideal protein" concept or formulation of balanced diets to maximize protein accretion and optimize health in animals and humans.
Given a nonlinear function h separating a convex and a concave function, we provide various conditions under which there exists an affine separating function whose graph is somewhere almost parallel to the graph of h. Such results blend Fenchel duality with a variational principle, and are closely related to the Clarke-Ledyaev mean value inequality. 1 Introduction The central theorems in this paper blend two completely distinct types of result, both fundamental in optimization theory: Fenchel duality and variational principles. The simplest version of Fenchel duality states that for any convex functions f and g on R n satisfying f Gammag, a regularity condition implies the set L def = fy 2 R n : f (y) + g (Gammay) 0g is nonempty (where f is the Fenchel conjugate of f ). Geometrically, this means there exists an affine function sandwiched between f and Gammag. On the other hand, one of the easiest examples of a variational principle states Keywords. Sandwich The...
The composition of free amino acids (FAAs) and nucleotides has an important effect on fish taste. In this study, the content of FAAs and nucleotides in raw, steamed, boiled and air-fried tilapia fillets were quantitatively analyzed. Thermal processing significantly influenced the composition of FAAs and nucleotides in tilapia. Moreover, there were substantial differences in the nutritional composition of tilapia processed by steaming, boiling and air frying. Compared with raw fillets, the total FAA (TFAA) increased after steaming, boiling, and air frying. The main umami and sweet amino acids in tilapia fillets were aspartic acid and glycine. The total nucleotide content of fresh tilapia was 299 mg/100 g, which increased to 305 and 366 mg/100 g after steaming and air frying, respectively, and decreased to 273 mg/100 g after boiling. The main taste nucleotide inosine monophosphate (IMP) with a taste activity value greater than 1, contributed greatly to the taste of tilapia. Equivalent umami concentration was used for taste evaluation: air frying > steaming > boiling. Therefore, our findings establish that the water-soluble taste substances of tilapia fillets, and the mutual regulatory effects of different compounds varied with different thermal processing methods. Hence, tilapia can be thermally processed according to different taste requirements.
The non‐thermal effects of microwave fields on the fatty acid composition of pasteurized Atlantic salmon were investigated using the same time‐temperature profiles method. Two pasteurization processes with same time‐temperature profiles were designed using a microwave processing system and a water bath. Then, the fatty acid composition of the processed salmon fillets was analyzed using the Gas Chromatography/Mass Spectrometry (GC/MS) method. Results showed that the time‐temperature profiles during microwave and water bath processing were well suited. With same time‐temperature profiles, the fatty acid compositions of salmon fillets processed by microwave and water bath were obviously different. Furthermore, microwave process brought better fatty acid quality in terms of higher values of n‐3 PUFA proportion, PUFA:SFA ratio, and lower n‐6 PUFA proportion. This demonstrated that microwave fields did have non‐thermal effects on the fatty acid composition of salmon with 3.5 min 8 kW microwave radiation and a final temperature of 90 ℃.
Microwave processing is a combined treatment of thermal and non-thermal effects on microorganisms and food ingredients. There may exist synergism between these two types of effects. The objective of this study was to explore the synergism of microwave thermal (i.e. temperature) and non-thermal effects on microbial inactivation and on fatty acids quality of pasteurized salmon fillets. Water bath processes with same time-temperature profiles and same microbial inactivation intensity were designed as control. Results showed that the microwave non-thermal effect on microbial inactivation was significantly (P < 0.05) enhanced by increasing temperatures. Compared with the microbial inactivation of thermal effect, the inactivation efficiency of microwave non-thermal effect increased from 22.18% to 35.25% while final temperatures of samples increased from 84 °C to 100 °C. Furthermore, with the same microbial inactivation intensity of 7.5-log CFU/g, microwave process retained better fatty acids quality in consideration of significantly higher (P < 0.05) PUFAs (especially for ARA, EPA and DHA) than those with water bath treatments. These results demonstrated that high temperatures could bring significant enhancement on microwave non-thermal effect, and microwave processing could provide better bacteria control and meanwhile retain higher product quality due to the synergism of microwave thermal and non-thermal effects.
Microwave processing has been a promising technology in improving quality and ensuring microbial safety of food products, while non-thermal effects of microwave is in controversy. The objective of this study was to investigate the non-thermal effects of microwave electromagnetic (EM) fields on Clostridium Sporogenes (surrogate of Clostridium botulinum) inoculated in salmon fillets using same time-temperature profiles method. The inoculated salmon fillets were processed by a single-mode pilot microwave processing system with different radiation time (2, 3 and 4 min) and holding time (0, 2 and 4 min). Corresponding water bath treatments were designed for each microwave processing to obtain matching time-temperature profiles. Results showed that the same time-temperature profiles method was successfully achieved to evaluate the microwave non-thermal effects in salmon fillets. With equal or lower thermal lethality value, microwave processing brought significantly higher (P < 0.05) reduction values than water bath treatment. This determined the non-thermal effects of microwave EM fields. And the non-thermal effects increased with longer microwave radiation time and was intensified by higher temperature. However, the following holding section will weaken the additional inactivation efficiency of microwave non-thermal effects. Results suggested that microwave processing could provide better bacteria control with lower thermal processing level.
In order to study the influence of microwave, especially nonthermal effect, on leather properties, the microwave was used to dry leather together with the oven dried leather as a control. The back, butt and belly of dried leathers were tested for mechanical properties, softness, shrinkage temperature, chrome and fat migration, microstructure and dielectric constant. The results showed that microwave could improve the mechanical properties, softness and shrinkage temperature as a visible nonthermal effect. The non-thermal effect could also promote uniformity of chrome tanning agent and fatliquoring agent in leather and strengthen combination of these materials with collagen. In addition, the fiber weaving of microwave dried leather was more orderly and porous proved by SEM and XRD. Furthermore, the dielectric constant of microwave dried leather was higher than control, showing a direct proof of non-thermal effect for microwave. To sum up, Microwave in leather drying has not only thermal effect but also non-thermal effect on improving leather overall performance.
This research investigated the application of 915 MHz microwaves in pasteurizing pre-packaged vegetables. A specially designed 915 MHz single-mode microwave-assisted pasteurization (MAP) system was used to process carrot cuboids in brine pre-packaged in 8-oz polymer pouches. Gellan gel was formulated and selected as the model food to simulate the real foods processed by the MAP system; heating patterns and cold spots of the pouched samples were detected by a chemical-marker based computer vision method. Two MAP processes (F90°C=3 min and F90°C=10 min) targeting Clostridium botulinum type E spores were developed and compared with conventional hot water (HW) processes resulting in equivalent microbial safety. Compared with an equivalent HW process, MAP process greatly reduced the total processing time, reduced the cook values and improved quality uniformity of the products. Quality evaluation showed the impacts of MAP processing on each quality attribute of carrot products depended on the specific quality parameter selected.
In this study, snapshots of operating frequency profiles of domestic microwave ovens were collected to reveal the extent of microwave frequency variations under different operation conditions. A computer simulation model was developed based on the finite difference time domain method to analyze the influence of the shifting frequency on heating patterns of foods in a microwave oven. The results showed that the operating frequencies of empty and loaded domestic microwave ovens varied widely even among ovens of the same model purchased on the same date. Each microwave oven had its unique characteristic operating frequencies, which were also affected by the location and shape of the load. The simulated heating patterns of a gellan gel model food when heated on a rotary plate agreed well with the experimental results, which supported the reliability of the developed simulation model. Simulation indicated that the heating patterns of a stationary model food load changed with the varying operating frequency. However, the heating pattern of a rotary model food load was not sensitive to microwave frequencies due to the severe edge heating overshadowing the effects of the frequency variations. The research work revealed the large frequency variations among domestic microwave ovens. The heating patterns of rotary solid model food loads were not sensitive to varying operating frequencies compared with those of stationary loads. This information should provide guidelines for product development in designing appropriate cooking instructions to ensure food safety.
The thermal effect of microwave radiation is well known. Based on the selective heating characteristics of microwave radiation, people have developed microwave ovens, microwave thawing equipments, drying and sterilization equipments, which are widely used in food processing. However, the question whether non-thermal effects of microwave radiation existed has always been the focus of debate. In recent years, researchers home and abroad took biological systems such as biological macromolecules or microorganisms as test objects to test and verify the non-thermal effects of microwave. From the current researches, the existence or not of the microwave non-thermal effects, is not ready to make a conclusion. The reason includes: the complexity of biological systems; the difficulty to control the temperature during the experiment; the lack of rationality and logic during experiment design. Whatever, the extensive and in-depth understanding of microwave non-thermal effects, is a reliable guarantee for the development of microwave equipments, and will create possibility for further application of microwave technology in deep processing of food products.
In this article, we prove an eigenvalue pinching theorem for the first
eigenvalue of the Laplacian on compact hypersurfaces in a sphere. Let $(M^n,g)$
be a closed, connected and oriented Riemannian manifold isometrically immersed
by $\phi$ into $\S^{n+1}$. Let $q>n$ and $A>0$ be some real numbers satisfying
$|M|^\frac{1}{n}(1+\|B\|_q)\leq A$. Suppose that $\phi(M)\subset B(p_0,R)$,
where $p_0$ is a center of gravity of $M$ and radius $R<\frac{\pi}{2}$. We
prove that there exists a positive constant $\e$ depending on $q$, $n$, $R$ and
$A$ such that if $n(1+\|H\|_\infty^2)-\e\leq \l_1$, then $M$ is diffeomorphic
to $\S^n$. Furthermore, $\phi(M)$ is starshaped with respect to $p_0$,
Hausdorff close and almost-isometric to the geodesic sphere $S\(p_0,R_0\)$,
where $R_0=\arcsin\frac{1}{\sqrt{1+\|H\|_\infty^2}}$.
In an attempt to find out new formation routes of possible reaction partners responsible for Strecker aldehyde formation in foods, this study describes the formation of phenylacetaldehyde in mixtures of phenylalanine with other amino acids upon heating. When phenylalanine was heated at 200 °C for 1 h in the presence of cysteine and serine, the formation of phenylacetaldehyde increased by 686 and 565%, respectively, in comparison to the phenylacetaldehyde produced by phenylalanine. This reaction, which was similarly produced by both amino acids as a function of reaction conditions (pH, amino acid concentration, reaction atmosphere, time and temperature), is suggested to be a consequence of the reaction between the carbonyl compounds produced by amino acid degradation and the phenylalanine. These results indicate that the amino acids cysteine and serine are able to contribute to the formation of Strecker aldehydes in foods, analogously to the previously described for carbohydrates and oxidized lipids. Nevertheless, the reaction has a relatively high Ea (91.5 and 102.6 kJ/mol for cysteine and serine, respectively). Therefore, it should only be expected to play a significant role in processes that require a high thermal input.
The amounts of ammonia released from thermal degradation of amino acids were measured using the ammonia electrode method. An aqueous solution of each amino acid was adjusted to pH 8 and heated at 180 degrees C for 2 h in a stainless steel reactor. Among the 19 amino acids studied, asparagine, aspartic acid, cysteine, and glutamine released large amounts of ammonia under the conditions employed. The effect of temperature on the generation of ammonia was studied for asparagine, asparatic, glutamine, glutamic acid, and cysteine.
We treat an extension of the generalized Fermat—Weber problem with convex cost functions. It is shown that the entire sequence of iterates (as opposed to selected subsequences) generated by each of the two proposed algorithms converges to a minimum although the economic function is not strictly convex. The general idea is to associate, with the economic function calledh, a family of more regular strictly convex functions, the lower envelope of which is the functionh.
The food processing industry has matured over the years with an impressive record on safety and a vibrant marketplace for new product development. Consumer demands for high-quality products has inspired researchers and the food industry to explore alternative methods as replacement for traditional processing methods. The food industry is poised to adopt cost effective technologies that offer better quality and safe products. Given the impressive safety record associated with traditional systems, one may be tempted to conclude that there is little room for advancement and innovation to meet current consumer demands. Process optimization will continue to evolve to enhance quality and overall energy utilization either in traditional or novel systems. The need for efficient operations will certainly drive system automation, control and monitoring systems that can handle complex mathematical routines in real-time. Such systems would certainly require vigorous validation and verification for industry to embrace them. It truly sounds illogical for industry to re-evaluate existing process schedules based on studies that demonstrate non-linearity of survival curves. However, the need to optimize quality and operating costs could potentially prompt re-evaluating existing systems to capture additional benefits. New processing concepts such as the application of variable retort temperature have received attention from processing experts and promises to improve both the economy and quality of thermally processed foods.
We present a simple and unified technique to establish convergence of various minimization methods. These contain the (conceptual) proximal point method, as well as implementable forms such as bundle algorithms, including the classical subgradient relaxation algorithm with divergent series.
Amino acid and proximate compositions were determined in six raw and cooked marine fish species that are commonly consumed in Turkey. The changes in amino acid and proximate content were found to be significant for all cooking methods in all fish species. Cooking did, in general, significantly increase the contents of essential, semiessential, and other amino acids compared with raw fish species. Grilled Atlantic bonito, anchovy, and bluefish and fried mullet and hake appeared to be more valuable fish dishes for obtaining the officially recommended appropriate daily intake of essential amino acids for humans. Moisture, fat, ash, and carbohydrate contents of raw fish ranged between 48.01% and 83.05%, 0.87% and 30.48%, 1.10% and 1.61%, and 0.09% and 8.70%, respectively. All fresh fish investigated were high in protein: 11.20-17.14 g/100 g. Wide variations in protein content (18.11-25.65 g/100 g) between species and methods of cooking were observed. Fried fish had intermediate fat values, whereas grilled and steamed fishes had a comparatively low value.
Plasma amino acids are usually analyzed by ion-exchange chromatography (IEC), a reproducible but time consuming method. Here, we test whether plasma amino acids can be analyzed using reverse-phase high performance liquid chromatography (HPLC).
Filtered plasma, with S-carboxymethyl-l-cysteine as the internal standard, was derivatized and analyzed by an Agilent 1100 HPLC system. Primary amino acids were derivatized with o-phthalaldehyde 3-mercaptopropionic acid (OPA) and detected by a diode array detector. Secondary amino acids were derivatized with 9-fluorenylmethyl chloroformate (FMOC) and detected fluorometrically. Chromatographic separation is achieved by two gradient elutions (two injections per sample), starting at different pHs, on a reverse phase Agilent Zorbax Eclipse C(18) column AAA (4.6 x 150 mm).
The HPLC method evaluated correlated well with IEC (0.89</=r</=1.00) with linearity up to 2500 mumol/l. The between- and within-run CVs were <6.0%. In addition, this method is able to separate argininosuccinic acid, homocystine and allo-isoleucine, rare but clinically significant amino acids.
This HPLC method was comparable to IEC and could represent an alternative for amino acid analysis.
The concept of nonthermal microwave effects has received considerable attention in recent years and is the subject of intense debate in the scientific community. Nonthermal microwave effects have been postulated to result from a direct stabilizing interaction of the electric field with specific (polar) molecules in the reaction medium that is not related to a macroscopic temperature effect. In order to probe the existence of nonthermal microwave effects, four synthetic transformations (Diels-Alder cycloaddition, alkylation of triphenylphosphine and 1,2,4-triazole, direct amide bond formation) were reevaluated under both microwave dielectric heating and conventional thermal heating. In all four cases, previous studies have claimed the existence of nonthermal microwave effects in these reactions. Experimentally, significant differences in conversion and/or product distribution comparing the conventionally and microwave-heated experiments performed at the same measured reaction temperature were found. The current reevaluation of these reactions was performed in a dedicated reactor setup that allowed accurate internal reaction temperature measurements using a multiple fiber-optic probe system. Using this technology, the importance of efficient stirring and internal temperature measurement in microwave-heated reactions was made evident. Inefficient agitation leads to temperature gradients within the reaction mixture due to field inhomogeneities in the microwave cavity. Using external infrared temperature sensors in some cases results in significant inaccuracies in the temperature measurement. Applying the fiber-optic probe temperature monitoring device, a critical reevaluation of all four reactions has provided no evidence for the existence of nonthermal microwave effects. Ensuring efficient agitation of the reaction mixture via magnetic stirring, no significant differences in terms of conversion and selectivity between experiments performed under microwave or oil bath conditions at the same internally measured reaction temperatures were experienced. The observed effects were purely thermal and not related to the microwave field.
We establish a mixed convex{Lipschitz mean value inequality from which recent results of Clarke and Ledyaev and of Lewis and Ralph follow naturally. We also provide various renements and extensions. Finally, we answer armatively several open questions on the existence of squeeze" theorems for a nite number of Lipschitz functions. AMS Classication Primary: 49J52, 90C25. Secondary: 26B25, 46N10, 47H10, 52A41. Key words Nonconvex separation, sandwich theorem, mean{value inequality, Fenchel duality, Schauder xed point theorem, Ekeland variational principle. 1 1. Introduction and Preliminaries Motivated by Clarke and Ledyaev's [2] striking multi-directional mean-value theorem and its elegant reformulation by Lewis and Ralph [8] as a non-smooth sandwich theorem, our intentions in this paper are two-fold. Firstly, in section two we provide a self-contained proof of a general convex/Lipschitz inequality from which both results follow. In section three we exploit the underlying techniqu...
Detection Amino Acids in Muscle of Hypophthalmichthys molitrix,Aristichthys nobilis and Ctenopharyngodon idellus by HPLC
- L I Yan
- Y Xie
- F H J H A S Yang
Yan, L. I., Xie, Y., & Yang, F. H. J. H. A. S. (2018). Detection Amino Acids in Muscle of
Hypophthalmichthys molitrix,Aristichthys nobilis and Ctenopharyngodon idellus by
HPLC.
Optimized preparation of Maillard reaction products from lysine and xylose and its antibacterial properties
- Wei-wei
Optimized preparation of Maillard reaction products from lysine and xylose and its antibacterial properties
- S Wei-Wei
- C Cao
- U Li-Ping
- D Sheng
- C Hao
- J Hao
- Z Jie
Wei-wei, S., Cao, C., Li-ping, U., Sheng, D., Hao, C., Hao, J., & Jie, Z. (2021). Optimized
preparation of Maillard reaction products from lysine and xylose and its antibacterial
properties. Food & Machinery, 1, 40-48.