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In this study, six lipase-producing strains from food sources were screened for their ability to produce lipase. Among them, Staphylococcus epidermidis N30 and Yarrowia lipolytica C11 demonstrated high enzyme activities of 1.07 and 0.84 U/mL, respectively. They had the following enzymatic properties: optimum reaction temperature of 50 ℃ and pH of 8.0. The optimum substrate for S. epidermidis N30 was C4 ester, while that for Y. lipolytica C11 was C8 ester. The inoculation of sour meat with S. epidermidis N30 or Y. lipolytica C11 effectively enhanced the production of flavor substances, especially ethyl butyrate, ethyl caproate, ethyl caprylate, ethyl caprate, nonanal and 1-octen-3-ol, thus promoting the production of fruity, floral, wine-like, mushroom-like and fatty aromas in sour meat.

BACKGROUND: To date, cider production has primarily relied on Saccharomyces cerevisiae. Introducing novel non‐Saccharomyces yeasts can enhance the diversity of cider properties. Among these, the Metschnikowia genus stands out for its ability to produce hydrolytic enzymes that may impact the sensorial and technological properties of cider. This study focused on evaluating the impact of three Metschnikowia species – Metschnikowia koreensis (Mk), M. reukaufii (Mr), and M. pulcherrima (Mp) – which exhibit acid protease and esterase activity, on the quality enhancement of cider. RESULTS: The research findings indicate that the overall quality of cider produced through co‐fermentation with these species surpassed that of cider fermented with mono‐fermentation of S. cerevisiae (Sc). The cider fermented with the Sc + Mk combination exhibited the lowest levels of harsh‐tasting malic acid and higher levels of softer lactic acid. Sensory array analysis also demonstrated that the Sc + Mk fermented cider exhibited high sensor response values for compounds contributing to a complex overall olfactory composition and richness. Furthermore, the Sc + Mk fermented cider exhibited the highest total quantity and variety of volatile organic compounds (VOCs). Specifically, the concentrations of phenethyl alcohol, 3‐methyl‐1‐butanol, ethyl octanoate, and decanoic acid were notably elevated in comparison with other groups. CONCLUSION: This study illustrates that Metschnikowia species, particularly M. koreensis, show significant potential as starters for cider due to their various technological properties, including acidity modulation, aroma enhancement, and color improvement. The findings of this study provide a foundation for improving cider quality by co‐fermenting S. cerevisiae with innovative starter cultures. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

To examine the variances in volatile organic compounds (VOCs) and sensory attributes across various hop cultivars, an analytical approach was employed. Specifically, gas chromatography-ion mobility spectroscopy (GC-IMS), gas chromatography-mass spectrometry (GC-MS), and quantitative descriptive analysis (QDA) were employed to scrutinize the VOCs and sensory characteristics of four distinct hop varieties, namely Magnum, Palisade, Saaz, and Hersbrucker. The outcomes of QDA revealed a diverse array of sensory profiles in the hops, encompassing citrus and non-citrus fruit aromas, woody, floral, herbal, spicy, and green aromas, with noticeable distinctions in sensory attributes discernible among the various hop cultivars. The results showed that 79 VOCs were identified in the GC-IMS spectra of different varieties of hops, including terpenes, alcohols, esters, aldehydes, and ketones. 140 VOCs were identified in the GC-MS spectra of different varieties of hops, including terpenes, alcohols, ketones, esters, acids, and aldehydes, with terpenes and esters emerging as the prevailing constituents in hops. The principal component analysis (PCA) of different hop VOCs was performed to effectively identify the differences among hop varieties. This study can provide a valuable reference for the comprehensive analysis of VOCs and sensory attributes in hops. Furthermore, it contributes theoretical underpinnings to inform the precise application of hops in the context of beer brewing. [ABSTRACT FROM AUTHOR]

Strong-flavor Daqu, as a fermentation agent, plays a significant role in shaping the quality of strong-flavor baijius, and fungal species in Daqu are important factors affecting the quality of Daqu. Therefore, we selected strong-flavor Daqu from seven different origins to study the fungal composition and the effects of the fungal composition on the physicochemical properties and volatile organic compounds (VOCs). It was found that the fungal composition influences the physicochemical properties of Daqu. Specifically, there was a positive link between Rhizomucor, Rhizopus, Thermomyces, and liquefying activity and a positive correlation between Aspergillus and fermenting activity. Furthermore, the relationships between esterifying activity and Thermomyces, Rhizomucor, Aspergillus, Pichia, and Saccharomycopsis were found to be positive. The VOCs in Daqu were affected by Aspergillus, Issatchenkia, Pichia, and Thermoascus. Issatchenkia was significantly positively correlated with benzeneethanol as well as Aspergillus and pentadecanoic acid ethyl ester, ethyl myristate. Pichia and Thermoascus were significantly negatively correlated with benzaldehyde and 2-furaldehyde. This study deepens our understanding of the relationship between VOCs, the physicochemical properties with microbial communities, and reference significance for the production of better-quality strong-flavor Daqu. [ABSTRACT FROM AUTHOR]

Cider flavor has a very important impact on the quality. Solid-phase microextraction-gas chromatography–mass spectrometry (SPME-GC-MS) combined with gas chromatography–ion mobility spectrometry (GC-IMS) tested different kinds of non-Saccharomyces yeasts and Saccharomyces cerevisiae (S. cerevisiae) co-inoculated for the fermentation of cider to determine differences in aroma material, and the determination of odor activity value (OAV) is applied less frequently in research. Through Rhodotorula mucilaginosa, Debaryomyces hansenii, Zygosaccharomyces bailii, and Kluyveromyces Marxianus, four different strains of non-Saccharomyces yeast fermented cider, and it was found that, in both the chemical composition and flavor of material things, compared with monoculture-fermented cider using S. cerevisiae, all differences were significant. Co-inoculated fermentation significantly improved the flavor and taste of cider. As in the volatile compounds of OVA > 1, octanoic acid (Sc 633.88 μg/L, co-inoculation fermented group 955.49 μg/L) provides vegetable cheese fragrance and decanoic acid, ethyl ester (Sc 683.19 μg/L, co-inoculation fermented group 694.98 μg/L) a creamy fruity fragrance, etc., and the average content increased after co-inoculated fermentation. Phenylethyl alcohol, which can produce a rose scent, was relatively abundant in cider samples and varied greatly among the groups. Moreover, the contents of ethyl lactate and 1-butanol in the Sc+Rm (ciders fermented by S. cerevisiae and R. mucilaginosa) were the highest of all of the cider samples. Different types of non-Saccharomyces yeast produced cider with different flavor characteristics. This study demonstrates that different species of non-Saccharomyces yeast do have an important impact on the characteristics of cider and that co-inoculation with non-Saccharomyces yeast and S. cerevisiae for cider fermentation may be a strategy to improve the flavor of cider. [ABSTRACT FROM AUTHOR]

Ethyl carbamate (EC), a 2A carcinogen produced during the fermentation of foods and beverages, primarily occurs in distilled spirits. Currently, most studies focus on strategies for EC mitigation. In the present research, we aimed to screen strains that can degrade EC directly. Here, we report two Candida ethanolica strains (J1 and J116), isolated from fermented grains, which can reduce EC concentrations directly. These two yeasts were grown using EC as the sole carbon source, and they grew well on different carbon sources. Notably, after immobilization with chitosan, the two strains degraded EC in Chinese Baijiu by 42.27% and 27.91% in 24 h (from 253.03 ± 9.89 to 146.07 ± 1.67 and 182.42 ± 5.05 μg/L, respectively), which was better than the performance of the non-immobilized strains. Furthermore, the volatile organic compound content, investigated using gas chromatography-mass spectrometry, did not affect the main flavor substances in Chinese Baijiu. Thus, the yeasts J1 and J116 may be potentially used for the treatment and commercialization of Chinese Baijiu. [ABSTRACT FROM AUTHOR]

BACKGROUND: Studies have shown that either the addition of starter culture or enzyme can improve fermentation in fish or other products. However, little research has been carried out on the effects of coupling starter cultures with lipase on the microbial community and product quality. Suanzhayu is a Chinese fermented fish product that mainly relies on spontaneous fermentation, resulting in an unstable flavor and quality. The present study investigated the impact of lipase and Lactiplantibacillus plantarum 1‐24‐LJ on the quality of Suanzhayu. RESULTS: Inoculation decreased pH and 2‐thiobarbituric acid reactive substances (TBARS) values, and also helped the dominance of the strain in the ecosystem, whereas lipase addition raised TBARS values and had little effect on pH, water activity (aw) and microbiota. The addition of lipase and/or Lpb. plantarum increased the content of alcohols, aldehydes, ketones, esters and umami amino acids. The co‐additions with the most significant effect and the total contents of volatile compounds (VCs) and free amino acids (FAAs) were 1801.92 g per 100 g and 21 357.05 mg per 100 g, respectively. Former‐Lactobacillus was negatively correlated with pH, aw and Prevotella, but positively with VCs (ethyl ester of heptanoic acid, ethyl ester of octanoic acid) and FAAs (Tyr, Phe). Furthermore, adding Lpb. plantarum 1‐24‐LJ alone or in combination with lipase shortened the fermentation process. CONCLUSION: The present study provides a recommended Suanzhayu process approach for improving product quality and flavor, as well as shortening fermentation time, by adding Lpb. plantarum 1‐24‐LJ with or without lipase. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The lactic acid bacteria (LABs) used for fermentation have an extremely vital impact on the quality of Suancai, a fermented vegetable. The bacterial diversity and metabolites of inoculated Suancai with LABs, including Lactiplantibacillus plantarum (Lb. plantarum), Levilactabacillus brevis (Lb. brevis), and Leuconostoc mesenteroides (Leu. mesenteroides), were investigated. The inoculation of LABs significantly decreased the pH and the content of nitrite. The Suancai inoculated with LABs had a higher content of the total titratable acidity (TTA) and organic acids than spontaneous fermentation. The LABs inoculation significantly influenced the bacterial community structures, which directly or indirectly caused changes of metabolites. The bacterial community profiles of Suancai inoculated with Lb. plantarum were more similar to spontaneous fermentation. The inoculation of Lb. plantarum, Lb. brevis, and Leu. mesenteroides could increase its abundance in Suancai. Whatever the species inoculated, Lb. plantarum was always the predominant bacterium in Suancai after fermentation. The inoculated LABs were positively correlated with most volatile compounds and amino acids. The inoculated LABs significantly improved the volatile compounds and amino acid content of Suancai. This study could contribute to understanding the function of starters in Suancai fermentation and promote the selection of applicable starters for high-quality Suancai production. [ABSTRACT FROM AUTHOR]

Biogenic amines (BAs) are produced by microbial decarboxylation in various foods. Histamine and tyramine are recognized as the most toxic of all BAs. Applying degrading amine enzymes such as multicopper oxidase (MCO) is considered an effective method to reduce BAs in food systems. This study analyzed the characterization of heterologously expressed MCO from L. sakei LS. Towards the typical substrate 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), the optimal temperature and pH for recombinant MCO (rMCO) were 25 °C and 3.0, respectively, with the specific enzyme activity of 1.27 U/mg. Then, the effect of different environmental factors on the degrading activity of MCO towards two kinds of BAs was investigated. The degradation activity of rMCO is independent of exogenous copper and mediators. Additionally, the oxidation ability of rMCO was improved for histamine and tyramine with an increased NaCl concentration. Several food matrices could influence the amine-oxidizing activity of rMCO. Although the histamine-degrading activities of rMCO were affected, this enzyme reached a degradation rate of 28.1% in the presence of surimi. Grape juice improved the tyramine degradation activity of rMCO by up to 31.18%. These characteristics of rMCO indicate that this enzyme would be a good candidate for degrading toxic biogenic amines in food systems. [ABSTRACT FROM AUTHOR]

Summary: Suanzhayu is a traditional Chinese fermented fish that often faces a long fermentation time (about 1 month) and unstable quality. This study evaluated the combined effects of papain and Lactiplantibacillus plantarum 1‐24‐LJ, a selected starter culture, on the quality of Suanzhayu. The addition of L. plantarum and/or papain increased the content of alcohols, esters, ketones and umami amino acids (UAAs), but decreased the content of bitter amino acids (BAAs). Besides, Lactobacillus might play a role in reducing harmful bacteria and BAAs content and increasing UAAs content, while Lactococcus and Weissella contributed to the characteristic flavour of Suanzhayu. Overall, no significant improvement in sensory quality was observed with the addition of papain alone, while better quality and faster fermentation processes were obtained with the addition of L. plantarum 1‐24‐LJ alone or in combination with papain. The results contribute to quality control in Suanzhayu production and the selection of starter cultures. [ABSTRACT FROM AUTHOR]

In this study, three Lactiplantibacillus plantarum, namely 3-14-LJ, M22, and MB1, with high acetate esterase activity, acid, salt, and high-temperature tolerance were selected from 708 strains isolated from fermented food. Then, L. plantarum strains MB1, M22, and 3-14-LJ were inoculated at 107 CFU/mL in the model and 107 CFU/g in actual Suanzhayu systems, and the effects during fermentation on the physicochemical properties, amino acid, and volatile substance were investigated. The results showed that the inoculated group had a faster pH decrease, lower protein content, higher TCA-soluble peptides, and total amino acid contents than the control group in both systems (p < 0.05). Inoculation was also found to increase the production of volatile compounds, particularly esters, improve the sour taste, and decrease the bitterness of the product (p < 0.05). L. plantarum M22 was more effective than the other two strains in stimulating the production of isoamyl acetate, ethyl hexanoate, and ethyl octanoate. However, differences were discovered between the strains as well as between the model and the actual systems. Overall, the isolated strains, particularly L. plantarum M22, have good fermentation characteristics and have the potential to become excellent Suanzhayu fermenters in the future. [ABSTRACT FROM AUTHOR]

Ethyl carbamate (EC), classified as a Group 2A carcinogen, is most abundant in the fermented foods, such as Cachaca, Shaoxing wine, and Chinese liquor (baijiu). Although biodegradation can reduce its concentration, a high ethanol concentration and acidic environment often limit its degradation. In the present study, a novel ethyl carbamate hydrolase (ECH) with high specificity to EC was isolated from Acinetobacter calcoaceticus, and its enzymatic properties and EC degradability were investigated. ECH was immobilized to resist extreme environmental conditions, and the flavor substance changes were explored by gas chromatography-mass spectrometry (GC/MS). The specific enzymatic activity of ECH was 68.31 U/mg. Notably, ECH exhibited excellent thermal stability and tolerance to sodium chloride and high ethanol concentration (remaining at 40% activity in 60% (v/v) ethanol, 1 h). The treatment of immobilized ECH for 12 h decreased the EC concentration in liquor by 71.6 μg/L. Furthermore, the immobilized ECH exerted less effect on its activity and on the flavor substances, which could be easily filtrated during industrial production. [ABSTRACT FROM AUTHOR]

The formation of soluble complexes between whey proteins and polysaccharides has potentially useful applications in the beverage industry. In this study, Auricularia auricula polysaccharides (AP) and A. auricula extract (EAA) were prepared and their complexation behavior with whey protein isolate (WPI) was studied at pH 4.7 in order to ensure protein dispersal and avoid precipitation to achieve enhanced WPI stability. Both AP and EAA enhanced stability of 2%–4% WPI via the formation of complexes. WPI‐AP and WPI‐EAA solutions exhibited characteristics resembling steady pseudoplastic fluid. Heat treatment further resulted in altered structures of formed complexes which improved stability. Sensory evaluation by electronic tongue indicated that AP and EAA could relieve astringency of the WPI solution induced in acidic pH. This study provided the theoretical basis and demonstrated the potential application of a novel WPI‐enriched beverage. Practical applications: Functional Auricularia auricula polysaccharides and an A. auricula extract were shown to enhance stability of high concentrated whey protein isolate solutions. In this study, a potential commercially exploitable healthy beverage was developed. Furthermore, the foundation for its production is provided, which does not involve polysaccharide extraction steps thereby preserving the nutritional value of polysaccharide‐rich ingredients. [ABSTRACT FROM AUTHOR]

BACKGROUND: Paocai is a traditional Chinese fermented vegetable food. As the most important ingredient, salt has crucial effects on the bacterial community and volatile compounds of paocai. To demonstrate the effects of salt on the fermentation of paocai, the bacterial composition and volatile compounds were investigated using high‐throughput sequencing and gas chromatography–mass spectrometry (GC–MS). RESULTS: The salt had no significant effects on the bacterial community at the phylum level. Proteobacteria and Bacteroidetes gradually decreased during the fermentation, and Firmicutes gradually increased as the dominant bacteria in the late stage of fermentation. At the genus level, Lactobacillus and Lactococcus gradually increased in relative abundance during the fermentation and became the dominant bacteria in paocai. High salt levels can contribute to the growth of Lactobacillus, which became the dominant genus in paocai. The salt concentration affected the profiles of volatile compounds in paocai after fermentation. A total of 42 volatile components were detected by GC–MS, among which phenols, aldehydes, and nitriles were the main ones. A high salt concentration will increase the volatile compound content, mainly aldehydes and alcohols, and improve the flavor of paocai. At the same time, the electronic tongue analysis also showed that a high salt concentration made a major contribution to the flavor of paocai. CONCLUSIONS: These data are helpful to elucidate the effects of salt on the quality of paocai and contribute to improving the quality and reducing the use of salt. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Toxic biogenic amines (BAs), especially histamine, in food is a major safety issue. Two autochthonous Lactobacillus plantarum strains were inoculated as starters to reduce BAs in Yucha, a kind of spontaneously fermented fish in China. Taxonomic analysis demonstrated the proportion of Lactobacillus genus in inoculated Yucha was higher than that in the spontaneously fermented Yucha, suggesting the effective colonization abilities of the starters. Higher abundance of Lactobacillus genus resulted in less BAs contents in the inoculated Yucha as compared to that in the spontaneously ones throughout the fermentation stage. At the end of fermentation, L. plantarum strains reduced total content of the six BAs by 67.5%–97.3%; specifically, they reduced the concentration of histamine by 85.4%–96.4%. The BAs‐degradation ability in the model systems indicated that the two L. plantarum strains could not degrade BAs directly. Instead, starters reduced BAs accumulation by inhibition of the growth or biological activities of BAs‐producing bacterial genera. Practical applications: The presence of biogenic amines (BAs) in fish products poses a health risk for consumers. This work provided two promising starters to reduce BAs accumulation in Yucha and a foundation for better understanding the BAs metabolic features. These findings could contribute to the safe production of Yucha and other similar fermented fish products. [ABSTRACT FROM AUTHOR]

Summary: The present study evaluated the relationship between the bacterial diversity and metabolites of various sour meats, a traditional fermented meat product. The results showed that sour meats had a low pH (average of 4.34), low water activity (aw, an average of 0.917), and high lactic acid (~19 177.48 mg kg−1) and free amino acid (FAA) (~4047.65 mg kg−1) concentrations. The lactic acid bacteria (LAB), especially Lactobacillus and Weissella, were predominated in the samples. The alcohols, aldehydes and esters accounted for the major components of volatile organic compounds (VOCs). Of which, (E)‐2‐octenal, nerol, cis‐4‐decenal, tetradecanal, linalyl acetate, linalool, 1‐octen‐3‐ol, hexanal, 1‐heptanol, benzaldehyde and (E)‐2‐decenal were considered as the key VOCs of sour meats. The redundancy analysis (RDA) and Pearson's correlation analysis revealed that LAB (Lactobacillus and Weissella) and salt were positively correlated with most FAAs and VOCs. Overall, higher salinity, lower aw and abundant LAB might be the indicators of good sour meat quality. [ABSTRACT FROM AUTHOR]

Rhodosporidium toruloides has been reported as a potential biotechnological microorganism to produce carotenoids. The most commonly used molecular and genetic manipulation methods based on Agrobacterium‐mediated transformation (ATMT). However, this method was of relatively lower transformation efficiency. In this study, we optimized the ATMT method for R. toruloides on account of the promoter on T‐DNA, the ratio of A. tumefaciens to R. toruloides NP11, acetosyringone concentration, cocultivation temperature and time, and a transformation efficiency of 2,369 cells per 105 recipient cells was obtained and was 24 times as that of the previous report. With this optimized method, four redder mutants and four yellower mutants were selected out with torularhodin and β‐carotene production preference, respectively. The highest torularhodin production was 1,638.15 µg/g dry cell weight in A1‐13. The yellower mutants were found to divert the metabolic flux from torularhodin and torulene to γ‐carotene and β‐carotene, and the proportion of γ‐carotene and β‐carotene were all over 92%. TAIL‐PCR was carried out to found T‐DNA insertion in these mutants, and insertion hotspot was found. RT‐qPCR results showed that CTA1 genes in these mutants were closely related to the synthesis of total carotenoids, especially torularhodin, and was a potenial metabolic engineering site in the future. [ABSTRACT FROM AUTHOR]

Summary: To mass‐produce nutritional kombucha with quality consistency, it is necessary to design synthetic microbial community (SMC) starters with clear bacterial compositions. In this study, a three‐species SMC, including Acetobacter pasteurianus, Gluconacetobacter xylinus and Zygosaccharomyces bailii, was designed. Acetic acid bacteria (AAB) in SMC produced a higher concentration of organic acids synergistically compared to each strain inoculated alone. Gluconic acid was the most abundant organic acid in kombucha fermented by SMC, which contributed to the pleasant sour taste of the beverage. AAB could also oxidise the alcohol produced by Z. bailii, making kombucha a soft beverage. Total phenol and flavonoid concentrations increased during fermentation, which enhanced the health benefits of kombucha. The sensory evaluation demonstrated tsshat sensory attributes of SMC fermented kombucha were quite similar to those fermented by the symbiotic culture of bacteria and yeast (SCOBY). Therefore, SMC could be utilised in the industrial mass production of kombucha for better quality control and product consistency. [ABSTRACT FROM AUTHOR]

Yucha is a home-made, fermented fish product in South China. The quality of yucha can vary depending on environmental factors. In order to determine the effects of temperature on bacterial biodiversity and quality of fermented yucha products, in the present study, yucha was fermented at 15°C, 20°C, 25°C, and 30°C. Bacterial cells in all yucha samples grew from 3.7 log CFU/g at the onset of the fermentation and reached growth over 7.0 log CFU/g within 1 week. Lactobacillus plantarum was predominated in the 20°C and 25°C fermented yucha products, while Lactobacillus sakei and Lactobacillus brevis were the most abundant in the yucha products fermented at 15°C and 30°C, respectively. Predominant bacterial species are presumed to be potential starters to drive yucha fermentation. Evaluation of yucha qualities demonstrated that lower biogenic amine contents, better texture properties, and more desirable volatile compounds were identified in yucha products fermented at 20°C. Therefore, this temperature is recommended for industrial yucha processing in the future. [ABSTRACT FROM AUTHOR]

To effectively extract biogenic amines (BAs) from complex food matrices is an important issue. In this study, a stop‐and‐go‐extraction tip (StageTip)‐based method for simultaneous enrichment of six BAs including histamine, tyramine, putrescine, cadaverine, tryptamine, and β‐phenylethylamine in fish samples was developed and optimized. This StageTip‐based BAs extraction method required short extraction time, small sample size, and minimal consumption of organic solvents. In addition, an ultrahigh‐performance liquid chromatography coupled with triple quadrupole mass spectrometer was used to identify and quantify BAs without derivatization. Target recovery efficiencies of BAs from spiked fish samples ranged from 84% to 110%. Linear regression models were established to determine BAs in the range of 0.4 to 3.0 mg/L (R2 > 0.995). Good repeatability was obtained with relative standard deviation of peak areas (1.17 to 5.61%) and retention time (0.09 to 0.20%). High sensitivity was achieved for the detection of six BAs (0.064 to 1.00 ng/L for the limit of detection, 0.10 to 5 ng/L for the limit of quantification). The proposed method had an obvious advantage in the analysis of BAs in complex food matrices such as fish tissues since it could reflect the subtle distribution of BAs from one fish fillet. Practical Application: A StageTip‐based BAs enrichment combined with UPLC‐MS analysis method was developed and optimized, which was low‐cost, environmentally friendly, and with good analytical performances. As such, it has the potential to become a powerful tool for the analysis of BAs in different complex food matrices. [ABSTRACT FROM AUTHOR]

The microbial community during the fermentation of industrial paocai, a lactic acid fermented vegetable food, was investigated via combined denaturing gradient gel electrophoresis (DGGE) and metagenomic sequencing. Firmicutes and Proteobacteria were identified as the dominant phyla during the fermentation. DGGE results of the bacterial community analysis showed that many genera were observed during the fermentation of industrial paocai, but the same predominant genus and species were observed: Lactobacillus and Lactobacillus (L.) alimentarius / L. paralimentarius. The abundance of L. alimentarius / L. paralimentarius increased fast during the initial stage of fermentation and approximately remained constant during the later stage. Metagenomic sequencing was used to finally identify the predominant species and their genetic functions. Metabolism was the primary functions of the microbial community in industrial paocai fermentation, including carbohydrate metabolism (CM), overview (OV), amino acid metabolism (AAM), nucleotide metabolism (NM), energy metabolism (EM), etc. The predominant species L. alimentarius and L. paralimentarius were involved in plenty of pathways in metabolism and played different roles in the metabolism of carbohydrate, amino acid, lipid to form flavor compounds during industrial paocai fermentation. This study provided valuable information about the predominant species in industrial paocai and its functional properties, which could enable us to advance our understanding of the fermentation mechanism during fermentation of industrial paocai. Our results will advance the understanding of the microbial roles in the industrial paocai fermentation and provide a theoretical basis for improving the quality of industrial paocai products. [ABSTRACT FROM AUTHOR]

The bacterial community in the pit mud of a Luzhou-flavour liquor distillery in different regions was analysed by combined polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and quantitative PCR (qPCR) in order to distinguish a matured and a degenerated pit mud, judged according to sensory and physicochemical characteristics. The phyla Firmicutes, Cloacimonetes, Actinobacteria, Proteobacteria, Synergistetes and Unclassified Bacteria were detected. Firmicutes predominated in the pit mud. The diversity and homogeneity of the bacterial community in the matured pit mud were superior to those in the degenerated pit mud in the same distillery. There were significant differences in the bacterial community structure between the matured and degenerated pit mud. Moreover, the bacterial community in the degenerated pit mud samples was similar, which indicated that the bacterial community in the degenerated pit mud did not change within the two different regions. However, the bacterial community in matured pit mud samples was different, demonstrating that there were visible differences in the bacterial community between the samples of matured pit mud collected from the Luzhou-flavour liquor distilleries in the two different regions. Notably, the quantity of Actinobacteria in the matured and the degenerated pit mud was found to be different by quantitative analysis. Potentially, the Actinobacteria could serve as an indicator bacteria to distinguish between matured and degenerated pit muds. Copyright © 2016 The Institute of Brewing & Distilling [ABSTRACT FROM AUTHOR]

BACKGROUND The community structure of bacteria in aged and aging pit mud, which was judged according to their sensory and physicochemical characteristics, was analysed using polymerase chain reaction denaturing gradient gel electrophoresis ( PCR-DGGE) and quantitative real-time PCR ( qPCR). RESULTS The phyla Firmicutes, Actinobacteria, Proteobacteria, Synergistetes and Unclassified Bacteria were detected and the fermentative Firmicutes was predominant in both types of pit mud in the PCR-DGGE analysis. Among Firmicutes, Clostridiales was dominant in aged pit mud while Bacillales and Lactobacillales were dominant in aging pit mud. The diversity of bacterial communities in aged pit mud was higher than that in aging pit mud. In the qPCR analysis the abundance of Clostridium IV in aged pit mud was higher than that in aging pit mud and there were significant differences in the quantity of Clostridium IV between aged and aging pit mud of the same cellar ( P < 0.05). CONCLUSION There were some significant differences in the microbial community structure between aged and aging pit mud. The differences in the quantity of Clostridium IV might be involved in the distinction that the aged pit mud has a strong aroma while the aging pit mud does not. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

This work investigated the effect of lipase addition on a Chinese traditional fermented fish product, Suanzhayu. The accumulation of lactic acid and the decrease of pH during the fermentation were mainly caused by the metabolism of Lactobacillus. The addition of lipase had little effect on pH and the bacterial community structure but promoted the growth of Proteus. The addition of lipase promotes the formation of volatile compounds, especially aldehydes and esters. The formation of volatile compounds is mainly divided into three stages, and lipase had accelerated the fermentation process. Lactobacillus, Enterococcus and Proteus played an important role not only in inhibition of the growth of Escherichia-Shigella, but also in the formation of flavor. This study provides a rapid fermentation method for the Suanzhayu process. [ABSTRACT FROM AUTHOR]

Suancai is a popular fermented product of Brassica vegetable in China. As important additive, salt concentration has crucial effects on the quality of suancai. To investigate the effects of salt concentration on suancai fermentation, the microbial diversity and volatile compounds (VCs) during fermentation were investigated by using Illumina HiSeq sequencing and GC-MS. Firmicutes, Proteobacteria and Ascomycota were detected as the main phylum during the fermentation with different salt concentrations. Lactobacillus , Lactococcus , Klebsiella , Weissella , Pediococcus , Candida , Cladosporium , Gibberella , Aspergillus , etc., were detected were observed during the fermentation with different concentrations. After fermentation, Lactobacillus predominated the fermentation of suancai and was not affected by salt concentration. Pediococcus , Leuconostoc , Weissella , Sporobolomyces , Azospirillum , Klebsiella , Acinetobacter and Cladosporium were significant affected by salt concentration. Salt addition could affect the VCs profiles and reduce the isothiocyanates after fermentation. Seventy-nine VCs were detected and strongly correlated with the dominant genus Lactobacillus during suancai fermentation. The inoculated fermentation of Lactobacillus could improve the VCs during fermentation. In conclusion, 6% salt addition could acquire a higher Lactobacillus abundance and a better taste quality. These results may facilitate the understanding of the effect of salt concentration on the fermentation ecology to improve suancai characteristics. • The 6% (w/w) salt addition was the best for suancai fermentation and quality. • Lactobacillus and unclassified fungus were dominant genera in suancai. • Seventy-nine VCs were detected during suancai fermentation with different salinity. • VCs were strongly correlated with Lactobacillus during suancai fermentation. • The inoculation of L. plantarum increased the VCs during suancai fermentation. [ABSTRACT FROM AUTHOR]

In this study, the electrospinning technique was used to co-encapsulate Quercetin (Qu) and Lactiplantibacillus plantarum 1–24-LJ in PVA-based nanofibers, and the effect of bioactive films on fish preservation was evaluated at the first time. The findings indicated that both Lpb. plantarum 1–24-LJ and Qu were successfully in the fibers, and co-loaded fibers considerably outperformed single-loaded fiber in terms of bacterial survival and antioxidant activity. Following fish preservation using the loaded fibers, significant reductions were observed in TVB-N, TBARS, and microbial complexity compared to the control group. Additionally, the co-loaded fibers more effectively reduced the counts of H 2 S-producing bacteria and Pseudomonas. In the future, fibers with both active substances and LAB hold promise as a novel approach for fish preservation. [Display omitted] • Co-loading of flavonoids quercetin (Qu) and Lpb. plantarum by electrospinning technology. • Qu and Lpb. plantarum synergize provide strong antioxidant and hyper-bacterial activity. • Qu or/and Lpb. plantarum films inhibit the growth of spoilage bacteria. • Active films improved fish's physiology, raised sensory appeal and extended storage time. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thermal oxidation mechanism of (E)−2-decenal was discussed by applying DFT. • Obtained reactions grouped into peroxide, alkoxy radical, peroxyl radical pathway. • Priority order is alkoxy radical > peroxide > peroxyl radical pathway. Unsaturated fatty aldehydes are the main products of fatty acid oxidation, and could be further oxidized to form volatile compounds with shorter carbon chains. Therefore, studying the oxidation of unsaturated fatty aldehydes is an important way to reveal the mechanism of food flavor formation during heating. In this study, volatile profiling of (E)-2-decenal during heating was firstly investigated by using thermal-desorption cryo-trapping combined with gas chromatography-mass spectrometry (GC–MS). A total of 38 volatile compounds were detected. Then, twenty-one reactions in the heating process of (E)-2-decenal were obtained by using density functional theory (DFT) calculations, and grouped into three oxidation pathways, namely, peroxide pathway, peroxyl radical pathway and alkoxy radical pathway. Meanwhile, the priority of these three pathways was the alkoxy radical reaction pathway > peroxide pathway > peroxyl radical reaction pathway. Moreover, the calculated results agreed well with the experimental results. [ABSTRACT FROM AUTHOR]