Analysis of volatile compounds in Xiangjiao baijiu from different storage containers and years based on HS-GC-IMS and DI-GC-MS

The volatile compounds in 16 different storage containers and years of Xiangjiao Baijiu (XJBJ) were compared and analyzed via direct injection (DI) combined with gas chromatography-mass spectrometry (GC-MS) and headspace extraction (HS) coupled with gas chromatography-ion mobility spectrometry (HS-GC-IMS) for the first time. Through HS-GC-IMS analysis, it was found that the succession rules of 14 compounds such as furfural during aging process. A total of 60 compounds were identified using DI-GC-MS. Twenty-five of these compounds were further quantified, and 19 compounds had odor activity values (OAVs) > 1, which were important contributor to aroma of XJBJ. Among them, those with OAVs >1000 included ethyl hexanoate, ethyl octanoate, ethyl butanoate, and ethyl pentanoate. Combining the results of quantitative, OAVs and partial least squares-discriminant analysis (PLS-DA) revealed that 10 compounds such as ethyl octanoate were the important compounds that lead to the differences between different storage types of XJBJ.

Effect of microbial communities on flavor profile of Hakka rice wine throughout production

Hakka rice wine is produced from grains by co-fermentation with abundant microbes in an open fermentation environment. Indigenous microbiota and enzymes convert the nutrients in grains into flavor compounds through enzymatic biochemical reactions and microbial metabolism. High-throughput sequencing technology revealed that non-Saccharomyces yeasts dominated the traditional fermentation process, with genera such as Kodamaea ohmeri, Candida orthopsilosis, and Trichosporon asteroides forming a dynamic community that highly correlated with the evolution of 80 volatile compounds in Hakka rice wine. Among the 104 volatile compounds detected by GC-MS, 22 aroma-active compounds with relative odor activity values (ROAV) > 1 were quantified, 11 of which made significant contributions (P < 0.05) to the overall aroma and were responsible for the sweet, grainy, and herbal aromas of Hakka rice wine.

Comparative study on key odorants of Jiujiang Fenggang Huangjiu and their succession regularities during aging using sensory-directed flavor analysis

Huangjiu was a Chinese national alcohol with a unique flavor. The key odorants in Jiujiang Fenggang Huangjiu (JJFG) and their succession regularities during aging were systematically researched by a sensomics analysis approach. The volatiles of JJFG were isolated by solvent-assisted flavor evaporation, 77 odorants were identified using gas chromatography-olfactometry-mass spectrometry combined with odor-specific magnitude estimation. Three aroma recombinants, prepared using odorants with odor activity values ≥ 1, all showed good similarities with their corresponding samples (92.1%∼97.5%). After omission/addition tests, 7 new key aroma compounds were found in JJFG, including 1-octen-3-one, 1-pentanol, guaiacol, ethyl 2-hydroxy-4-methylpentanoate, 2-phenethyl acetate, ethyl butanoate, and (E,Z)-2,6-nonadienal. Using orthogonal partial least squares-discriminant analysis, 20 compounds with VIP ≥ 1 were found to be important indicators during aging of JJFG. Among them, sotolon, 3-methylsulfanylpropanal, et al. increased with aging. The improved solid-phase extraction can effectively quantify sotolon, with a recovery rate of 80.96%∼91.75%.

Integrated meta-omics approaches reveal Saccharopolyspora as the core functional genus in huangjiu fermentations

Identification of the core functional microorganisms in food fermentations is necessary to understand the ecological and functional processes for making those foods. Wheat qu, which provides liquefaction and saccharifying power, and affects the flavor quality, is a key ingredient in ancient alcoholic huangjiu fermentation, while core microbiota of them still remains indistinct. In this study, metagenomics, metabolomics, microbial isolation and co-fermentation were used to investigate huangjiu. Although Aspergillus is usually regarded as core microorganism in wheat qu to initiate huangjiu fermentations, our metagenomic analysis showed that bacteria Saccharopolyspora are predominant in wheat qu and responsible for breakdown of starch and cellulose. Metabolic network and correlation analysis showed that Saccharopolyspora rectivirgula, Saccharopolyspora erythraea, and Saccharopolyspora hirsuta made the greatest contributions to huangjiu's metabolites, consisting of alcohols (phenylethanol, isoamylol and isobutanol), esters, amino acids (Pro, Arg, Glu and Ala) and organic acids (lactate, tartrate, acetate and citrate). S. hirsuta J2 isolated from wheat qu had the highest amylase, glucoamylase and protease activities. Co-fermentations of S. hirsuta J2 with S. cerevisiae HJ resulted in a higher fermentation rate and alcohol content, and huangjiu flavors were more similar to that of traditional huangjiu compared to co-fermentations of Aspergillus or Lactiplantibacillus with S. cerevisiae HJ. Genome of S. hirsuta J2 contained genes encoding biogenic amine degradation enzymes. By S. hirsuta J2 inoculation, biogenic amine content was reduced by 45%, 43% and 62% in huangjiu, sausage and soy sauce, respectively. These findings show the utility of Saccharopolyspora as a key functional organism in fermented food products.

Directionally controlling flavor compound profile based on the structure of synthetic microbial community in Chinese liquor fermentation

Most traditional fermented foods are produced by spontaneous fermentation. It is difficult to produce traditional fermented foods with desired flavor compound profile. In this study, using Chinese liquor fermentation as a case, we aimed to directionally control flavor compound profile in food fermentation. Twenty key flavor compounds were identified in 80 Chinese liquor fermentations. Six microbial strains, identified as high producers of these key flavor compounds, were used to generate the minimal synthetic microbial community. A mathematical model was established to link the structure of the minimal synthetic microbial community and the profile of these key flavor compounds. This model could generate the optimal structure of synthetic microbial community to produce flavor compounds with desired profile. This work provided a strategy to realize the directional control of flavor compound profile via controlling the structure of the synthetic microbial community in Chinese liquor fermentation.

Effect of Koji on Flavor Compounds and Sensory Characteristics of Rice Shochu

Koji is an important starter for rice shochu brewing and influences the rice shochu quality. Consequently, we studied the impacts of koji on the flavor compounds and sensory characteristics of rice shochu using molds Aspergillus kawachii SICC 3.917 (A-K), Aspergillus oryzae SICC 3.79(A-O), Aspergillus Niger CICC 2372 (A-N), Rhizopus oryzae CICC 40260 (R-O), and the traditional starter Qu (control). The effects of koji on the aroma components, free amino acids (FAAs), and overall sensory aspects of rice shochu were studied. These findings indicated that koji significantly affected the rice shochu’s quality. The content of total FAAs in rice shochu A-K (30.586 ± 0.944 mg/L) and A-O (29.919 ± 0.278 mg/L) was higher than others. The content of flavor compounds revealed that the aroma of rice shochu with various koji varied greatly from the smells of alcohols and esters. Shochu A-O had a higher concentration of aroma compounds and it exhibited a strong aroma and harmonious taste compared with the others. This research using taste compounds, FAAs, flavor intensity, and partial least squares regression (PLSR) showed that shochu A-O appeared to possess the best sensory qualities, with elevated concentrations of alcohols and sweet FAAs and lesser concentrations of sour FAAs. Therefore, the A-O mold is promising for the manufacture of rice shochu with excellent flavor and sensory characteristics.

Comparison of Fermentation Behaviors and Characteristics of Tomato Sour Soup between Natural Fermentation and Dominant Bacteria-Enhanced Fermentation

In this study, the correlations between microbial communities with physicochemical properties and volatile flavor compounds (VFCs) during the fermentation of traditional tomato sour soup (CTN) are explored. The results of high-throughput sequencing (HTS) of CTN showed that Lacticaseibacillus (28.67%), Enterobacter (12.37%), and Providencia (12.19%) were the dominant bacteria in the first round of fermentation, while Lacticaseibacillus (50.11%), Enterobacter (13.86%), and Providencia (8.61%) were the dominant bacteria in the second round of fermentation. Additionally, the dominant fungi genera of the first fermentation were Pichia (65.89%) and Geotrichum (30.56%), and the dominant fungi genera of the second fermentation were Pichia (73.68%), Geotrichum (13.99%), and Brettanomyces (5.15%). These results indicate that Lacticaseibacillus is one of the main dominant bacteria in CTN. Then, the dominant strain Lacticaseibacillus casei H1 isolated from CTN was used as a culture to ferment tomato sour soup to monitor dynamic changes in the physicochemical properties and VFCs during enhanced fermentation of tomato sour soup (TN). The physicochemical analysis showed that, compared with CTN, the TN group not only produced acid faster but also had an earlier peak of nitrite and a lower height. The results of the GC–IMS analysis showed that the ester and alcohol contents in the TN group were 1.26 times and 1.8 times that of the CTN group, respectively. Using an O2PLS-DA analysis, 11 bacterial genera and 18 fungal genera were identified as the functional core flora of the CTN group flavor production, further verifying the importance of dominant bacteria for the production of VFCs. This study proved that enhanced fermentation not only shortens the fermentation cycle of tomato sour soup, but also significantly improves its flavor quality, which has great value in the industrial production of tomato sour soup and in the development of a vegetable fermentation starter.

Unraveling the difference in aroma characteristics of Huangjiu from Shaoxing region fermented with different brewing water, using descriptive sensory analysis, comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry and multivariate data analysis

To investigate the specific difference in aroma characteristics of Huangjiu (Chinese rice wine) in Shaoxing region fermented with different brewing water, descriptive sensory analysis, comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry (GC × GC-qMS) and multivariate statistical analysis were employed. The descriptive sensory analysis proved that Huangjiu fermented with Jianhu water had higher overall aroma intensity, and was more prominent in ester, sweet and alcoholic aroma than those fermented with deionized water and Nenjiang water. The results of aroma components analysis by GC × GC-qMS showed that the Huangjiu fermented with Jianhu water had higher concentration of some key aroma compounds, such as ethyl butyrate (OAV: 29-196), isoamyl acetate (OAV: 11-18) and ethyl hexanoate (OAV: 38-47). The multivariate statistical analysis further confirmed that 14 compounds could be used as key markers to distinguish the Huangjiu samples fermented with different brewing water. The correlation network between the volatile compounds in Huangjiu and the inorganic components in water indicated that the ions played an important role in the formation of the difference in aroma characteristics among the samples.

Metagenomics-based insights into the microbial community profiling and flavor development potentiality of baijiu Daqu and huangjiu wheat Qu

Daqu and wheat Qu are saccharification and fermenting agents in Chinese huangjiu and baijiu production. This study aimed to investigate the difference between Daqu and wheat Qu in physicochemical indices, microbial communities, functional genes, and the metabolic network of key microbes responsible for flavor synthesis by whole-metagenome sequencing and metabolite analysis. Herein, physicochemical indices indicated that compared with wheat Qu, Daqu exhibited higher protease and cellulase activity and acidity, and lower glucoamylase and amylase enzyme activity. Metagenomic sequencing reveals that although Daqu and wheat Qu community composition have significant differences at species level, they have similar functional genes. Daqu were enriched in Pediococcus pentosaceus, Weissella paramesenteroides, Rasamsonia emersonii and Byssochlamys spectabilis (22.48% of the total abundance), while wheat Qu harbored greater abundances of Saccharopolyspora (54.78%, Saccharopolyspora rectivirgula, Saccharopolyspora shandongensis, Saccharopolyspora hirsuta, Saccharopolyspora spinose, and Saccharopolyspora erythraea). From a functional perspective, the important functions of Daqu and wheat Qu are both amino acid metabolism and carbohydrate metabolism. Meanwhile, a combined analysis among microbiota, functional genes, and dominant flavors indicated S. shandongensis, S. rectivirgula, and S. spinose might be the main contributor to the synthesis of flavor compounds in wheat Qu, while R. emersonii, W. paramesenteroides, Leuconostoc citreum, Leuconostoc mesenteroides, Weissella cibaria and P. pentosaceus may make the greatest contribution to flavor compounds synthesis in Daqu. This study reveals the microbial and functional dissimilarities of Daqu and wheat Qu, and helps elucidating different metabolic roles of microbes during flavor formation.

The sensory and flavor characteristics of Shaoxing Huangjiu (Chinese rice wine) were significantly influenced by micro-oxygen and electric field

In order to improve the high cost of equipment and difficult management caused by the natural aging of Chinese rice wine (Huangjiu), micro-oxygen (MO) and electric field (PEF) technology are used to accelerate the aging of Huangjiu. The results showed that micro-oxygen and electric field have a significant effect on the sensory characteristics and flavor characteristics of Huangjiu. Compared with the naturally aged Huangjiu, the flavor compounds of Huangjiu treated with micro-oxygen and electric field increase significantly. Based on principal component analysis, Huangjiu processed at 0.35 mg L/day or 0.5 mg L/day combined electric field exhibited similar flavor to the natural aged Huangjiu, which was highly associated with long-chain fatty acid ethyl esters (C13-C18). Moreover, partial least squares regression demonstrated that sensory attributes of cereal aroma and astringency were highlighted after aging time, while fruit aroma, continuation, and full body were dominant after micro-oxygen and electric field treatment. Micro-oxygen and electric field effectively enhanced the quality of Huangjiu, which could be applied in other alcoholic beverages.

Development of a novel multi-strain wheat Qu with high enzyme activities for Huangjiu fermentation

BACKGROUND

Wheat Qu has long been used as a fermentation starter to produce Huangjiu. Wheat Qu quality depends on its microbial community structure and the hydrolytic enzymes generated by the micro-organisms.

RESULTS

Strain YF1 and YF2 were successfully screened as they exhibited high acidic protease (231.9 ± 1.4 U g^-1 ) and cellulase (7.1 ± 0.6 U g^-1 ) activities. Based on a morphological and sequence analysis of the internal transcribed spacer (ITS) gene, YF1 and YF2 were identified as Rhizopus oryzae and Aspergillus niger, respectively. Cooked wheat Qu was produced using mixed fungal starter fermentations with Aspergillus oryzae SU-16, YF1, and YF2. For Qu-making, the optimized conditions for fermentation time, water content, and inoculum size were 47.8 h, 69.4%, and 6.1%, respectively. Under these conditions, compared with single-strain cooked wheat Qu, enzyme activities of amylase, acidic protease, and cellulase increased by 27.4%, 657.1%, and 1276.2%, respectively. Short peptides and free amino acids contents increased by 19.6% and 131.8%, respectively. This wheat Qu was used for Huangjiu brewing, and the alcohol content increased by approximately 14.6% because of the increased starch hydrolysis efficiency mainly attributed to its high enzyme activity.

CONCLUSION

Using mixed fungal strains as starter cultures may be an efficient strategy to improve wheat Qu quality, with great potential for application in industrial Huangjiu production. © 2021 Society of Chemical Industry.

Peptides in Brewed Wines: Formation, Structure, and Function

The traditional low-alcoholic beverages, such as grape wine, sake, and rice wine, have been consumed all over the world for thousands of years, each with their unique methods of production that have been practiced for centuries. Moderate consumption of wine is generally touted as beneficial for health, although there is ongoing debate for the responsible components in wine. In this review, the structural and functional characteristics, the formation mechanisms, and their health-promoting activities of peptides in three brewed wines, grape wine, Chinese rice wine (also called Chinese Huangjiu or Chinese yellow wine), and Japanese sake, are discussed. The formation of peptides in wine imparts sensorial, technological, and biological attributes. Prospects on future research, with an emphasis on the peptide characterization, formation mechanism, physiological activity, and molecular mechanisms of action, are presented.

Flavor Formation in Chinese Rice Wine (Huangjiu): Impacts of the Flavor-Active Microorganisms, Raw Materials, and Fermentation Technology

Huangjiu (Chinese rice wine) has been consumed for centuries in Asian countries and is known for its unique flavor and subtle taste. The flavor compounds of Huangjiu are derived from a wide range of sources, such as raw materials, microbial metabolic activities during fermentation, and chemical reactions that occur during aging. Of these sources, microorganisms have the greatest effect on the flavor quality of Huangjiu. To enrich the microbial diversity, Huangjiu is generally fermented under an open environment, as this increases the complexity of its microbial community and flavor compounds. Thus, understanding the formation of flavor compounds in Huangjiu will be beneficial for producing a superior flavored product. In this paper, a critical review of aspects that may affect the formation of Huangjiu flavor compounds is presented. The selection of appropriate raw materials and the improvement of fermentation technologies to promote the flavor quality of Huangjiu are discussed. In addition, the effects of microbial community composition, metabolic function of predominant microorganisms, and dynamics of microbial community on the flavor quality of Huangjiu are examined. This review thus provides a theoretical basis for manipulating the fermentation process by using selected microorganisms to improve the overall flavor quality of Huangjiu.

Contribution of autochthonous yeasts with probiotic potential to the aroma profile of fermented Guajillo pepper sauce

BACKGROUND

Three yeast strains with probiotic potential, Hanseniaspora opuntiae, Pichia kudriavzevii, and Wickerhamomyces anomalus were inoculated in the fermentation of Guajillo chilli pepper (Capsicum annuum L.) sauce, and the different aroma profiles were investigated. Using headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) analysis and gas chromatography-olfactometry (GCO), flavour compound production was evaluated during the fermentation of the Guajillo chilli pepper sauces.

RESULTS

A total of 78 volatile compounds were identified during the yeast fermentation of the sauce. Most aldehydes and terpenes detected were present at the beginning of the fermentation, indicating a Guajillo chilli pepper origin. Among the 34 active aroma compounds detected by GCO, propanoic acid (cheesy), 3-methylbutanoic acid (sharp, cheese), ethyl 2-methylbutanoate (fruity), and 6-methyl-5-hepten-2-one (strong, citrus) were identified as key aroma contributors produced by the inoculation of the yeasts. A different aroma profile was produced by probiotic yeast. Hanseniaspora opuntiae produced an aroma profile with herbal and green notes based on high production of aldehydes, ketones, and acetic acid. Pichia kudriavzevii and W. anomalus produced fruity, green-herbal, and cheesy notes based on ester compounds, alcohol and branched-chain acids production although, the production of propanoic acid by W. anomalus increased the cheesy character in the sauces.

CONCLUSION

The aroma profile of fermented chilli pepper sauces depends not only on the chili pepper varieties used but also on the fermentation process as a source of aroma compounds. The use of probiotic yeast can be used to improve and diversify the aroma profile of fermented chilli pepper sauces. © 2020 Society of Chemical Industry.

Age-dependent characterization of volatile organic compounds and age discrimination in Chinese rice wine using an untargeted GC/MS-based metabolomic approach

An untargeted gas chromatography/mass spectrometry (GC/MS)-based metabolomics by XCMS-Online software combined with partial least squares regression (PLSR) was applied to characterize volatile organic compounds (VOCs) during Chinese rice wine aging and discriminate ages for the first time. Finally, seven different ages between 0 and 15 years were well discriminated by PLSR. Total 104 feature groups were isolated from all optimized candidate peaks, and 94 VOCs (including unknowns) were preliminarily identified as aging markers. Therein, alcohols, sulfides, phenols and their derivatives, small esters and acids exhibited significantly better discrimination of short-aged rice wines. Correspondingly, furans, aromatics, aldehydes, ketones, most esters and acids, discriminated the long-aged samples better. Meanwhile, the potential origins of certain VOCs were also proposed for further research. Overall, this untargeted GC/MS-based metabolomics coupled with PLSR was a feasible tool for a rapidly and globally age-dependent characterization of volatile metabolomic signals in Chinese rice wine and thus for age discrimination.

Effects of aging on the quality of roasted sesame-like flavor Daqu

Background

Daqu, the saccharification, fermentation, and aroma-producing agents for Baijiu brewing, is prepared using a complex process. Aging is important for improving the quality of Daqu, but its impact has rarely been studied. This study investigated changes in the physicochemical properties, flavor compounds, and microbial communities during aging of Daqu with a roasted sesame-like flavor.

Results

The physicochemical properties changed continuously during aging to provide a high esterifying activity. Aging removed unpleasant flavor compounds and helped to stabilize the flavor compounds in mature Daqu. A high-throughput sequencing approach was used to analyze the changing composition of the microbial communities during aging. Aging helped to modify the microbial population to produce better Baijiu by eliminating low-abundance microbial communities and optimizing the proportion of predominant microbial communities. Nine genera of prokaryotic microbes formed the core microbiota in Daqu after aging. Regarding eukaryotic microbes, Zygomycota, the predominant community, increased in the first 2 months, then decreased in the third month of aging, while Ascomycota, the subdominant community, showed the opposite behavior. Absidia, Trichocomaceae_norank and Rhizopus were the predominant genera in the mature Daqu.

Conclusions

Significant correlations between microbiota and physicochemical properties or flavor compounds were observed, indicating that optimizing microbial communities is essential for aging Daqu. This study provides detailed information on aging during Daqu preparation.

Characterization of the volatile profile of Chinese rice wine by comprehensive two-dimensional gas chromatography coupled to quadrupole mass spectrometry

BACKGROUND

Chinese rice wine (CRW) is a kind of traditional fermentation wine in China. Aged CRW is more popular among consumers owing to its harmonious and pleasant flavor. The volatile profile of CRW has been extensively studied using gas chromatography/mass spectrometry (GC/MS). However, flavor components in CRW are far richer than those detected by GC/MS. To obtain more information about the volatile profile of fresh (5-year) and aged (10-year) CRW, a method based on comprehensive two-dimensional gas chromatography coupled to quadrupole mass spectrometry (GC×GC/qMS) was developed. The major volatile compounds contributing to the characteristic aroma of fresh and aged CRW were identified by surrogate odor activity value (OAV).

RESULTS

Ninety-eight volatile compounds were detected in the 5-year CRW samples and 107 in the 10-year samples by GC×GC/qMS. The numbers of compounds detected by GC×GC/qMS for the 5-year and 10-year samples were 71.4 and 65.4% higher than those detected by GC/MS. The aged wine had a more complex volatile profile than the fresh wine, with an increase in esters and aldehydes and a decrease in alcohols and organic acids. There were 22 volatile compounds with surrogate OAV > 1. Nine were the potent key aroma compounds in CRW: ethyl isovalerate (OAV 500-33 500), ethyl butyrate (OAV 84-334), ethyl isobutyrate (OAV 49-170), 2-nonenal (OAV 20-100), ethyl heptanoate (OAV 1-74), ethyl hexanoate (OAV 60-77), phenylethyl alcohol (OAV 2-18), benzaldehyde (OAV 28-30) and hexanal (OAV 4-11).

CONCLUSION

GC×GC/qMS showed better separation than GC/MS. The presented GC×GC/qMS method was suitable for characterization of the volatile profile of CRW. © 2019 Society of Chemical Industry.

Mucor indicus and Rhizopus oryzae co-culture to improve the flavor of Chinese turbid rice wine

BACKGROUND

One of the most important species used to ferment Chinese turbid rice wine (CTRW) at an industrial-scale level is Rhizopus oryzae, although the flavor of CTRW fermented by pure R. oryzae is inferior to that of traditional CTRW.

RESULTS

Mucor indicus was used as a cooperative species to improve the flavor of CTRW presented by R. oryzae. The flavor compounds in different fermentation stages were determined by headspace solid-phase microextraction-gas chromatography-mass spectrometry and high-performance liquid chromatography. It was noted that the M. indicus and R. oryzae co-culture changed the profiles of flavor compounds in CTRW, including esters, higher alcohols, amino acids and organic acids, and also significantly enhanced the concentration of sweet amino acids, fruity and floral esters, and higher alcohols. Sensory evaluation demonstrated that the CTRW fermented by M. indicus and R. oryzae had a more intense aroma, harmonious taste, continuation and full body mouth-feel because of more abundant flavor compounds.

CONCLUSION

Mucor indicus is a promising species for co-culture with R. oryzae to improve the flavor of CTRW. © 2019 Society of Chemical Industry.

Distinctive Formation of Volatile Compounds in Fermented Rice Inoculated by Different Molds, Yeasts, and Lactic Acid Bacteria

Rice has been fermented to enhance its application in some foods. Although various microbes are involved in rice fermentation, their roles in the formation of volatile compounds, which are important to the characteristics of fermented rice, are not clear. In this study, diverse approaches, such as partial least squares-discriminant analysis (PLS-DA), metabolic pathway-based volatile compound formations, and correlation analysis between volatile compounds and microbes were applied to compare metabolic characteristics according to each microbe and determine microbe-specific metabolites in fermented rice inoculated by molds, yeasts, and lactic acid bacteria. Metabolic changes were relatively more activated in fermented rice inoculated by molds compared to other microbes. Volatile compound profiles were significantly changed depending on each microbe as well as the group of microbes. Regarding some metabolic pathways, such as carbohydrates, amino acids, and fatty acids, it could be observed that certain formation pathways of volatile compounds were closely linked with the type of microbes. Also, some volatile compounds were strongly correlated to specific microbes; for example, branched-chain volatiles were closely link to Aspergillus oryzae, while Lactobacillus plantarum had strong relationship with acetic acid in fermented rice. This study can provide an insight into the effects of fermentative microbes on the formation of volatile compounds in rice fermentation.

Comparison of Volatile and Nonvolatile Compounds in Rice Fermented by Different Lactic Acid Bacteria

The production of rice-based beverages fermented by lactic acid bacteria (LAB) can increase the consumption of rice in the form of a dairy replacement. This study investigated volatile and nonvolatile components in rice fermented by 12 different LABs. Volatile compounds of fermented rice samples were analyzed using gas chromatography-mass spectrometry (GC-MS) combined with solid-phase microextraction (SPME), while nonvolatile compounds were determined using gas chromatography-time-of-flight/mass spectrometry (GC-TOF/MS) after derivatization. The 47 identified volatile compounds included acids, aldehydes, esters, furan derivatives, ketones, alcohols, benzene and benzene derivatives, hydrocarbons, and terpenes, while the 37 identified nonvolatile components included amino acids, organic acids, and carbohydrates. The profiles of volatile and nonvolatile components generally differed significantly between obligatorily homofermentative/facultatively heterofermentative LAB and obligatorily heterofermentative LAB. The rice sample fermented by Lactobacillus sakei (RTCL16) was clearly differentiated from the other samples on principal component analysis (PCA) plots. The results of PCA revealed that the rice samples fermented by LABs could be distinguished according to microbial strains.

Characterization of key aroma compounds in Chinese rice wine using gas chromatography-mass spectrometry and gas chromatography-olfactometry

To determine the key aroma compounds in Chinese rice wine (CRW), four types of CRW (YH, JF, SN, and XX) were analyzed by gas chromatography-mass spectrometry (GC-MS), gas chromatography-olfactometry (GC-O), and sensory evaluation. The contributions of the key aroma compounds to the flavor characteristics were determined by partial least squares regression. Sixty-one aroma compounds were detected. Twenty-five components were identified as odor-active compounds. On the basis of their odor active values, 18 odor-active compounds were determined as key aroma compounds. Ethyl isovalerate, ethyl butyrate, ethyl acetate, ethyl hexanoate, and phenylethyl alcohol were key aroma compounds in all four types of wine. The unique key aroma compounds of JF wine were isovaleraldehyde and isoamyl acetate; those of XX wine were 1-butanol, benzaldehyde, ethyl benzoate, ethyl phenylacetate, 2-octanone, and furfural; that of YH wine was ethyl 2-methylbutyrate; and those of SN wine were 1-butanol, 1-hexanol, 2-butenoic acid ethyl ester, and 3-methyl-1-butanol.

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.

Main parameters and the dynamics of volatile compounds during the fermentation of Chinese Mao-tofu from Huangshan region

The physico-chemical parameters and kinetics of the volatile compounds during the fermentation of Chinese Mao-tofu was investigated. The levels of water soluble proteins, amino nitrogen and acidity increased gradually throughout the fermentation process, while that of reducing sugars peaked after 2 days before gradually declining. The protease activity increased significantly and reached the maximum levels at day 3, then it slightly decreased. The hardness and firmness decreased during the first 3 days, but both increased subsequently. The viscosity and adhesiveness was inversely related to the hardness and firmness. Forty-four volatile compounds were identified and quantified. Correlation analysis revealed significant correlation of the content of water soluble proteins and amino nitrogen with most volatile compounds. Acidity levels were positively correlated with that of ethyl caproate and hexyl alcohol, and negatively with 2-methyl butyric acid, palmitic acid, ethyl laurate, 1-octen-3-ol and 1-nonanol. Reducing sugar content was also positively correlated with ethyl caproate.

Characterization of the Key Aroma Compounds in Proso Millet Wine Using Headspace Solid-Phase Microextraction and Gas Chromatography-Mass Spectrometry

The volatile compounds in proso millet wine were extracted by headspace solid-phase microextraction (85 μm polyacrylate (PA), 100 μm polydimethylsiloxane (PDMS), 75 μm Carboxen (CAR)/PDMS, and 50/30 μm divinylbenzene (DVB)/CAR/PDMS fibers), and analyzed using gas chromatography-mass spectrometry; the odor characteristics and intensities were analyzed by the odor activity value (OAV). Different sample preparation factors were used to optimize this method: sample amount, extraction time, extraction temperature, and content of NaCl. A total of 64 volatile compounds were identified from the wine sample, including 14 esters, seven alcohols, five aldehydes, five ketones, 12 benzene derivatives, 12 hydrocarbons, two terpenes, three phenols, two acids, and two heterocycles. Ethyl benzeneacetate, phenylethyl alcohol, and benzaldehyde were the main volatile compounds found in the samples. According to their OAVs, 14 volatile compounds were determined to be odor-active compounds (OAV > 1), and benzaldehyde, benzeneacetaldehyde, 1-methyl-naphthalene, 2-methyl-naphthalene, and biphenyl were the prominent odor-active compounds (OAV > 50), having a high OAV. Principal component analysis (PCA) showed the difference of distribution of the 64 volatile compounds and 14 odor-active compounds with four solid-phase microextraction (SPME) fibers.

Innovation Chinese rice wine brewing technology by bi-acidification to exclude rice soaking process

As a traditional fermented alcoholic beverage of China, Chinese rice wine (CRW) had a long history of more than 5000 years. Rice soaking process was the most crucial step during CRW brewing process, because rice soaking quality directly determined the quality of CRW. However, rice soaking water would cause the eutrophication of water bodies and waste of water. The longer time of rice soaking, the higher the content of biogenic amine, and it would have a huge impact on human health. An innovation brewing technology was carried out to exclude the rice soaking process and the Lactobacillus was added to make up for the total acid. Compared to the traditional brewing technology, the new technology saved water resources and reduced environmental pollution. The concentration of biogenic amine was also decreased by 27.16%, which improving the security of the CRW. The esters increased led to more soft-tasted CRW and less aging time; the quality of CRW would be improved with less alcohol.

Extraction optimization of polysaccharides from Chinese rice wine from the Shaoxing region and evaluation of its immunity activities

BACKGROUND

Chinese rice wine is well known for its unique flavor and high nutritional value. It is of interest to investigate the functional components of Chinese rice wine and their health benefits.

RESULTS

Response surface design of three factors - pH, ethanol concentration and precipitation time - at three levels was utilized to optimize the extraction of Chinese rice wine polysaccharide (CRWP). The results indicated that the CRWP yield was 77.287% at the optimal levels for pH 8.4, ethanol concentration 88% and precipitation time 23 h. In addition, immune activity of CRWP was investigated by measuring body weight, spleen index and thymus index. Furthermore, immunity activity of CRWP was investigated by measuring lymphocyte proliferation, phagocytic index and phagocytic percentage of immunosuppressed mice. Compared with the control mice and model mice, it was found that CRWP has beneficial immune activities in vivo.

CONCLUSION

These findings indicate that CRWP has immune activities in vivo by modulating the immune response, and implies full development and utilization of the nutritional value of Chinese rice wine. However, further work will be conducted in the future to elucidate the structure-bioactivity relationship for CRWP.

Development of a colorimetric sensor array for the discrimination of Chinese liquors based on selected volatile markers determined by GC-MS

A new colorimetric sensor array was developed for the discrimination of 12 high-alcoholic Chinese base liquors from Luzhou Co., Ltd., and 15 commercial Chinese liquor of different brands as well as flavor types. Seventeen volatile compounds within four chemical groups were determined as markers in the base liquor by GC-MS analysis and factor analysis method (FAM). A specialized colorimetric sensor array composed of 20 sensitive dots was fabricated accordingly to obtain sensitive interaction with different types of volatile markers. Discrimination of the liquor samples was subsequently performed using chemometric and statistical methods, including principal component analysis (PCA) and hierarchical clustering analysis (HCA). The results suggested that facile identification of either base liquors with high-alcoholic volume or commercial liquors of the same flavor types could be achieved by analysis of the color change profiles. The response of the sensor improved significantly in comparison with those that rely on nonspecific interactions, and no misclassification was observed for both liquor samples using two chemometric methods. Besides, it was also found that the discrimination is closely related to the characteristic flavor compounds (esters, aldehydes, and acids) and alcoholic strength in liquors, and its performance was even comparable with that of GC-MS.