Formation Of Flavor Compounds Research Articles

A Systems-Wide Analysis of Proteolytic and Lipolytic Pathways Uncovers The Flavor-Forming Potential of The Gram-Positive Bacterium Macrococcus caseolyticus subsp. caseolyticus.

Macrococcus caseolyticus subsp. caseolyticus is a Gram-positive, commensal organism documented to be present as a component of the secondary microflora in fermented foods such as Ragusano and Fontina cheeses and Cantonese sausage. In these products, the organism appears to play a role in ripening and the development of the final organoleptic qualities. However, the role of this organism in flavor generation is not well understood. Therefore, the objective of this study was to investigate the role of M. caseolyticus subsp. caseolyticus in flavor compound formation through an examination of enzymatic, metabolomic and genomic data. A bank of M. caseolyticus subsp. caseolyticus strains derived from a variety of niches were examined. Enzyme activities analyzed comprised those of the proteolytic and lipolytic cascades including cell-envelope proteinase (CEP), peptidases, esterases, lipases, aminotransferases and glutamate dehydrogenase (GDH). Strain to strain variation was observed, often associated with niche. All strains, except those isolated from non-dairy sources, demonstrated high CEP activity. Such high CEP activity associated with dairy strains implies the importance of this characteristic in the adaptation of these strains to a dairy-specific niche. However, limited downstream peptidolytic activity, in addition to a limited ability to generate free amino acids (FAA) was observed across all strains, indicating weak ability of this organism to generate amino-acid derived flavor compounds. Interestingly, the strains with high CEP activity also demonstrated high esterase activity and gas chromatography-mass spectrometry (GC-MS) analysis of the volatile compounds produced when these strains were grown in lactose-free milk demonstrated differences in the range and types of volatiles produced. In contrast to this metabolic versatility, comparative genome analysis revealed the distribution of components of the proteolytic and lipolytic system in these strains to be conserved. Overall, this study demonstrates the potential of M. caseolyticus subsp. caseolyticus to generate diverse volatile flavor compounds. Additionally, the identification of the highly active strain-specific cell wall bound caseolytic proteases deriving extensive casein hydrolysis, serves as a promising avenue which can be potentially harnessed in the future to produce greater and more diverse flavor compounds.

Correlations between microbiota succession and flavor formation during fermentation of Chinese low-salt fermented common carp (Cyprinus carpio L.) inoculated with mixed starter cultures

The correlation between microbiota succession and flavor development in Chinese traditional fermented fish (Suanyu) inoculated with mixed starter cultures was studied. The results showed that 17 free amino acids, 22 free fatty acids and 9 organic acids were present. A total of 81 aroma compounds were detected during Suanyu fermentation. Aldehydes were the most abundant aroma compounds in the early stage of fermentation and esters contributed most to the aroma in the later stage of fermentation. The correlation analysis of microbial succession and flavor dynamics based on bidirectional orthogonal partial least squares (O2PLS) suggested that in addition to starter cultures, other microorganisms including 2 bacteria genera and 11 fungi genera were also responsible for the formation of flavor compounds. These results may help focus further research to improve the flavor quality of traditional fermented fish.

Fully Automated Identification of Coffee Species and Simultaneous Quantification of Furfuryl Alcohol Using NMR Spectroscopy.

Coffee is a popular beverage with two species, Coffea canephora and C. arabica, being commercially exploited. The quality and commercial value of coffee is dependent on species and processing. C. arabica typically obtains a higher price on the market compared to C. canephora. Coffee beans undergo roasting during processing, resulting in the formation of flavor compounds including furfuryl alcohol which has been classified by the International Agency for Research on Cancer as possibly carcinogenic to humans (Group 2B). The aim of this study was to identify coffee species and other properties using nuclear magnetic resonance (NMR) spectroscopy, specifically to conduct quantification of the roasting process contaminant furfuryl alcohol. The quantification of furfuryl alcohol was performed from the NMR spectra using the pulse length-based concentration (PULCON) methodology. Prior to NMR analysis, samples were extracted using deuterated chloroform. Roasting experiments identified the maximum roasting temperature to be the most significant factor in the formation of furfuryl alcohol. Among the coffee species, C. canephora was found to contain a relatively lower amount of furfuryl alcohol compared to C. arabica. The roasting of wet processed coffee resulted in higher contents of furfuryl alcohol. Geographical origin and variety within species had no influence on the furfuryl alcohol content. Validation results show that NMR spectroscopy is fit-for-purpose to obtain targeted information of coffee samples. The PULCON NMR methodology allows a simple, rapid and accurate determination of constituents of coffee.

Effect of Weissella cibaria co-inoculation on the quality of Sichuan Pickle fermented by Lactobacillus plantarum

The effect of Weissella cibaria co-inoculation on the quality of Sichuan Pickle (SCP) fermented by Lactobacillus plantarum was evaluated. The fresh cowpea and seasoning ingredients were sterilized firstly by 70% (v/v) edible alcohol solution, and then respectively fermented with W. cibaria or L. plantarum or their mixed inoculums in brine containing 6.0% salt for 7 days at 25 °C. The cell growth, pH, non-volatile organic acids, volatile flavor compounds, residual nitrite and biogenic amines were monitored during fermentation. Compared to mono-inoculation of L. plantarum, co-inoculation accelerated cell proliferation, pH decrease and production of non-volatile organic acids in initial fermentation, and also significantly promoted the formation of volatile flavor compounds in types and contents during fermentation, especially for the aroma-active and key volatile compounds, thus improved the overall sensory quality of SCP. Furthermore, the co-inoculation decreased the concentration of nitrite and biogenic amines by 5–12% and 6–12%, respectively. Therefore, co-inoculating W. cibaria has improved the food quality of SCP fermented by mono-inoculation of L. plantarum.

Effect of green tea catechins on physical stability and sensory quality of lactose-reduced UHT milk during storage for one year

Ultra-high temperature (UHT) processed lactose-reduced milk containing added green tea extract (GTE) at two concentrations (0.1% and 0.25%) was stored at 22 ± 2 °C for one year. The effect of GTE addition on physical stability, protein binding, and sensory quality was evaluated. Sedimentation in skim milk and creaming of full fat milk were inhibited by addition of GTE. The formation of Maillard-related flavour compounds was inhibited during storage as determined by dynamic headspace GC–MS. Using Western blot analysis, milk proteins were found to be highly conjugated to polyphenols. Addition of GTE before UHT treatment resulted in increased bitterness and astringency in UHT milk and this remained during storage. Even though GTE addition improved the physical stability and inhibited Maillard reactions in the milk, the taste and flavour contribution from GTE was dominating throughout storage, and alternative sources of polyphenols should be explored for increasing shelf-life stability of long-life milk.

The changes of microbial community and flavor compound in the fermentation process of Chinese rice wine using Fagopyrum tataricum grain as feedstock

Chinese rice wine (CRW), a unique wine species, has a long history in China. Fagopyrum tataricum grain is a kind of high-quality grain with function in health care. The production of CRW wine with F. tataricum grain is beneficial to the development of new rice wine products. The flavor compounds and microorganisms in F. tataricum grain rice wine were studied. One hundred and seven volatile compounds (including 11 kinds of pyrazines that were rarely detected in wine) were detected and eight organic acids were measured. The microecological diversity in the fermentation process of F. tataricum rice wine was studied. It was found that Bacillus was the main bacterial genus, and the unclassfied_O_Saccharomycetales was the main fungi. Correlation analysis between microorganism and flavor compound shown there are 838 correlations. A total of 108 microbial genera maybe participate in the formation of flavor compounds. In addition, fourteen genera included unclassified_O_Saccharomycetales, Lactococcus, Pediococcus, Aspergillus, Cladosporium, Cochliobolus, Sporidiobolus, Pichia and Saccharomycopsis et al. were screened as functional significant microbiota and built correlation with flavor compounds. This work provides a perspective for bridging the gap between flavor compound and microbial community, and advances our understanding of mechanisms in F. tataricum rice wine fermentation.

Symposium review: Genomic investigations of flavor formation by dairy microbiota

Flavor is one of the most important attributes of any fermented dairy product. Dairy consumers are known to be willing to experiment with different flavors; thus, many companies producing fermented dairy products have looked at culture manipulation as a tool for flavor diversification. The development of flavor is a complex process, originating from a combination of microbiological, biochemical, and technological aspects. A key driver of flavor is the enzymatic activities of the deliberately inoculated starter cultures, in addition to the environmental or "nonstarter" microbiota. The contribution of microbial metabolism to flavor development in fermented dairy products has been exploited for thousands of years, but the availability of the whole genome sequences of the bacteria and yeasts involved in the fermentation process and the possibilities now offered by next-generation sequencing and downstream "omics" technologies is stimulating a more knowledge-based approach to the selection of desirable cultures for flavor development. By linking genomic traits to phenotypic outputs, it is now possible to mine the metabolic diversity of starter cultures, analyze the metabolic routes to flavor compound formation, identify those strains with flavor-forming potential, and select them for possible commercial application. This approach also allows for the identification of species and strains not previously considered as potential flavor-formers, the blending of strains with complementary metabolic pathways, and the potential improvement of key technological characteristics in existing strains, strains that are at the core of the dairy industry. An in-depth knowledge of the metabolic pathways of individual strains and their interactions in mixed culture fermentations can allow starter blends to be custom-made to suit industry needs. Applying this knowledge to starter culture research programs is enabling research and development scientists to develop superior starters, expand flavor profiles, and potentially develop new products for future market expansion.

Effect of the Calpain System on Volatile Flavor Compounds in the Beef Longissimus lumborum Muscle.

The present study was designed to investigate the effects of calpain system on the formation of volatile flavor compounds in Hanwoo beef. In the first experiment (exp.1), Longissimus lumborum (LL) muscle samples were injected with solutions containing 50 mM CaCl2 or 50 mM ZnCl2 and 154 mM NaCl respectively, and aged for 7 d at 4°C. In the second experiment (exp.2), the ground LL muscle was incubated with the aforementioned solutions containing cathepsin inhibitor. The injection with CaCl2 solution greatly elevated the calpain activity and concomitantly, significantly decreased the Warner-Bratzler shear force (p<0.05). The pH, meat color and cooking loss did not differ (p>0.05) between the treatment groups. A total of 51 volatile compounds were identified using the solid phase microextraction with gas chromatography (SPME-GC). Results on volatile analyses from the both experiments showed that the injection with calcium ions led to significant increase (p<0.05) concentrations of pyrazines and sulfuric compounds. These results coincide with a higher rate of protein degradation due to the CaCl2 injection as compared to the control group. Significantly (p<0.05) higher levels of lipid oxidation derived-aldehydes were found in the samples with ZnCl2. The exp.1 showed that cathepsin inhibitors had no effect on the formation of volatile flavor components after 7 d of aging. These results imply that the proteolytic activity of the calpain system is associated with generation of volatile compounds of chiller-aged beef, while the role of cathepsins is likely very limited.

Effect of Microwave Vacuum Drying on the Drying Characteristics, Color, Microstructure, and Antioxidant Activity of Green Coffee Beans

The aim of this study is to investigate the effect of microwave vacuum drying (MVD) on the drying characteristics and quality attributes of green coffee beans. We specifically focused on the effective moisture diffusion coefficient (Deff), surface temperature, glass transition temperature (Tg), water state, and microstructure. The kinetics of color changes during drying, total phenolic content (TPC), and antioxidant activity (DPPH, FRAP, and ABTS) were also characterized. Microwave power during MVD affected the porosity of coffee beans, their color, TPC, and antioxidant activity. The Allometric 1 model was the most suitable for simulating surface temperature rise kinetics. Thermal processing of green coffee beans resulted in increased b*, L*, ΔE, and TPC values, and greater antioxidant capacity. These findings may provide a theoretical reference for the technical improvement, mechanisms of flavor compound formation, and quality control of dried green coffee beans.

Application of Microbial Enzymes in Dairy Products: A Review

Enzymes produced by microbial sources are biological molecules that known to catalysts biochemical reactions which roles involve in lead to stimulate the necessary chemical reactions, as well as to the formation of fermented products. Microbial protease, lipase and ?-galactosidase are important examples of such interest in industrial food and dairy product. This is due to their thermoresistant, thermostability and thermoacidophilic properties. In brief, hydrolyses are the substrate which includes some enzymatic reaction that allows to avoid the health and environmental problems, and also to catalyses chemical reaction during the formation of flavor compounds or prebiotic and other products additives in the production and development of healthy dairy food products. Thus, enzymes are one of the relatively important factor that expected to be utilized in large-scale in the process of products development. This review focused on the importance and application of three major enzymes that microbial produce which are of great interest in dairy industries and have positive impact on consumer’s health.

Application of Microbial Enzymes in Dairy Products: A Review

Enzymes produced by microbial sources are biological molecules that known to catalysts biochemical reactions which roles involve in lead to stimulate the necessary chemical reactions, as well as to the formation of fermented products. Microbial protease, lipase and β-galactosidase are important examples of such interest in industrial food and dairy product. This is due to their thermoresistant, thermostability and thermoacidophilic properties. In brief, hydrolyses are the substrate which includes some enzymatic reaction that allows to avoid the health and environmental problems, and also to catalyses chemical reaction during the formation of flavor compounds or prebiotic and other products additives in the production and development of healthy dairy food products. Thus, enzymes are one of the relatively important factor that expected to be utilized in large-scale in the process of products development. This review focused on the importance and application of three major enzymes that microbial produce which are of great interest in dairy industries and have positive impact on consumer’s health.

Maillard volatiles in baked products as affected by feruloylated oligosaccharides from maize bran

ABSTRACTFeruloylated oligosaccharides (FOs) have been approved by the US Food and Drug Administration to be incorporated in baked goods. This research aimed to investigate the influence of FOs on flavour formation. Results revealed that the furfural content increased 5.2-, 6.7-, 5.6-, and 6.5-fold after 10 mg/g FOs was added and by 6.7-, 37.8-, 12.4-, and 64.5-fold after 50 mg/g FOs was added to aspartic acid/glucose, asparagine/glucose, glutamic acid/glucose, and dough models, respectively. Addition of FOs prevented the formation of favourable Maillard flavour compounds, such as pyrazines, maltol, nonanal, and cedrol, but produced unpleasant flavour compounds, such as dimethyl disulphide, dimethyl trisulphide, and 2-methoxy-4-vinylphenol. Our findings suggest that the addition of FOs to thermally processed food should be evaluated with caution.

Management of Multiple Nitrogen Sources during Wine Fermentation by Saccharomyces cerevisiae.

During fermentative growth in natural and industrial environments, Saccharomyces cerevisiae must redistribute the available nitrogen from multiple exogenous sources to amino acids in order to suitably fulfill anabolic requirements. To exhaustively explore the management of this complex resource, we developed an advanced strategy based on the reconciliation of data from a set of stable isotope tracer experiments with labeled nitrogen sources. Thus, quantifying the partitioning of the N compounds through the metabolism network during fermentation, we demonstrated that, contrary to the generally accepted view, only a limited fraction of most of the consumed amino acids is directly incorporated into proteins. Moreover, substantial catabolism of these molecules allows for efficient redistribution of nitrogen, supporting the operative de novo synthesis of proteinogenic amino acids. In contrast, catabolism of consumed amino acids plays a minor role in the formation of volatile compounds. Another important feature is that the α-keto acid precursors required for the de novo syntheses originate mainly from the catabolism of sugars, with a limited contribution from the anabolism of consumed amino acids. This work provides a comprehensive view of the intracellular fate of consumed nitrogen sources and the metabolic origin of proteinogenic amino acids, highlighting a strategy of distribution of metabolic fluxes implemented by yeast as a means of adapting to environments with changing and scarce nitrogen resources.IMPORTANCE A current challenge for the wine industry, in view of the extensive competition in the worldwide market, is to meet consumer expectations regarding the sensory profile of the product while ensuring an efficient fermentation process. Understanding the intracellular fate of the nitrogen sources available in grape juice is essential to the achievement of these objectives, since nitrogen utilization affects both the fermentative activity of yeasts and the formation of flavor compounds. However, little is known about how the metabolism operates when nitrogen is provided as a composite mixture, as in grape must. Here we quantitatively describe the distribution through the yeast metabolic network of the N moieties and C backbones of these nitrogen sources. Knowledge about the management of a complex resource, which is devoted to improvement of the use of the scarce N nutrient for growth, will be useful for better control of the fermentation process and the sensory quality of wines.

Controlled formation of flavor compounds by preparation and application of Maillard reaction intermediate (MRI) derived from xylose and phenylalanine

An effective method for preparing Maillard reaction intermediate (MRI) derived from xylose (Xyl) and phenylalanine (Phe) in aqueous medium was proposed in this study.

Identification of the Volatile Compounds in the roasting Venezuela Criollo cocoa beans by Gas Chromatography-Spectrometry Mass

An identification of the volatile compounds from the fermented dried and toasted (at 20 °C, 25 minutes) cocoa beans from a population of selected cocoa, were studied. The selected material “Criollo” (205 trees) was gathered from the plantation “El Pedregal” located at the south of Maracaibo Lake, Rio Frio “ Merida state, Venezuela. The volatile fraction was extracted and analyzed by gas chromatography coupled to a mass spectrometer (SPME/MS). The goal of the researching was the quantification of the content of organic volatile compounds developed by effect of the cocoa roasting. Volatile identification was performed comparing the retention indices and mass spectra obtained with those of the compounds existing as reference in the bank of the “Wiley Mass Spectral Data”. Sixty-nine volatile compounds that were grouped into 12 chemical families were identified. Aldehydes, alcohols, acids, hydrocarbons, pyrazines and diverse compounds, were the compounds prevalent in the volatile fraction of roasted cocoa. As conclusion this research permits the establishment of the identification and sensory quality of the Venezuelan creole cocoa, is of consensus that the volatile profile of the Venezuelan cocoa, which is highly appreciated by the chocolatiers of the world, has been fewer studied. It is also observed that there is an effect of post-harvest treatment (fermentation, drying) and roasted on the formation of flavor compounds in the fraction of roasted cacao. The results of these studies also show that SPME has a significant advantage over more traditional methods for analysis of volatile compounds in the cocoa beans post-harvest process: no fermented, fermented, dried and roasted.

Functional genomics provides insights into the role of Propionibacterium freudenreichii ssp. shermanii JS in cheese ripening

Propionibacterium freudenreichii is a commercially important bacterium that is essential for the development of the characteristic eyes and flavor of Swiss-type cheeses. These bacteria grow actively and produce large quantities of flavor compounds during cheese ripening at warm temperatures but also appear to contribute to the aroma development during the subsequent cold storage of cheese. Here, we advance our understanding of the role of P. freudenreichii in cheese ripening by presenting the 2.68-Mbp annotated genome sequence of P. freudenreichii ssp. shermanii JS and determining its global transcriptional profiles during industrial cheese-making using transcriptome sequencing. The annotation of the genome identified a total of 2377 protein-coding genes and revealed the presence of enzymes and pathways for formation of several flavor compounds. Based on transcriptome profiling, the expression of 348 protein-coding genes was altered between the warm and cold room ripening of cheese. Several propionate, acetate, and diacetyl/acetoin production related genes had higher expression levels in the warm room, whereas a general slowing down of the metabolism and an activation of mobile genetic elements was seen in the cold room. A few ripening-related and amino acid catabolism involved genes were induced or remained active in cold room, indicating that strain JS contributes to the aroma development also during cold room ripening. In addition, we performed a comparative genomic analysis of strain JS and 29 other Propionibacterium strains of 10 different species, including an isolate of both P. freudenreichii subspecies freudenreichii and shermanii. Ortholog grouping of the predicted protein sequences revealed that close to 86% of the ortholog groups of strain JS, including a variety of ripening-related ortholog groups, were conserved across the P. freudenreichii isolates. Taken together, this study contributes to the understanding of the genomic basis of P. freudenreichii and sheds light on its activities during cheese ripening.

Changes in Protein Hydrolysates During Processing of Chinese Traditional Dry-Cured Bacon (Laròu) Production

Protein and its degradation products are the main nutrients and flavor precursors in pork products. In this study, protein, total nitrogen (TN), water-soluble nitrogen (WSN), peptides, and free amino acids (FAAs) were analyzed during the production process of Chinese traditional dry-cured bacon, “Laròu.” Results indicated that the TN content showed no significant changes throughout the whole process, while the WSN content decreased sharply during the salting period but increased during aging. The sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) profile indicated that protein decomposition effectively took place during the late aging period. A decreasing tendency of the total peptides was observed throughout the aging period. On the contrary, the content of total FAAs increased significantly in the final products. Protein degradation and related flavor compound formation mostly occurred during the aging period of the “Laròu” manufacturing. Practical Applications “Laròu” is a popular Chinese dry-cured meat product for its special chewiness and flavor. This study investigates the changes in proteolysis during the process of “Laròu” and provides the theoretical bases for the quality improvement of Chinese traditional dry-cured meat products.

Multiple roles of lactic acid bacteria microflora in the formation of marker flavour compounds in traditional chinese paocai

Traditional paocai brine (PB), which is continuously propagated by back-slopping and contains multiple species of lactic acid bacteria (LAB), is critical for the flavour of paocai.

Effects of nitrogen catabolite repression-related amino acids on the flavour of rice wine

The quality of rice wine is highly dependent on the content of the flavour compounds produced by the budding yeast Saccharomyces cerevisiae. In this study, the effects of three amino acids (arginine, glutamate and glutamine) related to nitrogen catabolite repression on the formation of flavour compounds were investigated. Each of these amino acids could promote the growth of S. cerevisiae, and a total of 83 flavour compounds were found in a model system of rice wine production. The effects of arginine, glutamate and glutamine on the content of the higher alcohols, amino acids and esters were significant, whereas the effects on the aldehydes and organic acids were slight. The results of this study could facilitate the development of new strategies to control the flavour pattern and improve the quality of rice wine. Copyright © 2015 The Institute of Brewing & Distilling

Quantitative analysis of predominant yeasts and volatile compounds in the process of pickled wax gourd

Yeasts have been reported to be responsible for flavor compound formation in, and the quality of, pickled wax gourd. In this study, the diversity of yeasts and their predominant species in pickled wax gourd, as well as the capability to produce aroma compounds were detected by 5.8 S rDNA-ITS clone library combined with RT-PCR technology and GC–MS. It showed the predominant yeast species in the pickling processing were Issatchenkia orientalis, Pichia kudriavzevii and Candida xylopsoci, and clones numbers of each yeast species reached 107 copies mL–1. A total of 66 volatile constituents were identified and quantified, and the major volatile compounds of pure culture with yeast were alcohols, which were the critical flavor composition of pickled wax gourd. Together, these results could provide information about the quality control of pickled wax gourd including the flavor composition and the growth of predominant microbial species.