Study on the Fermented Grain Characteristics and Volatile Flavor Substances during the Tuqu Fermentation of Hunan Light-Flavor Baijiu.

The present study employed Hunan local Tuqu for fermentation and investigated the physicochemical properties, microbial community composition, and volatile flavor compounds of the fermented grains, as well as the correlation between the physicochemical indicators and the microbial community. The findings reveal that the activities of α-amylase and glucoamylase were highest during the initial stages of the fermentation process. The acid protease activity increased to 30.6 U/g on the second day and then decreased. Cellulose and lipase activities both showed an increasing trend. The moisture content increased sharply to 73.41% and then remained relatively stable. The acidity was highest on the eighth day. Fifty genera of bacteria and twenty-two genera of fungi were detected. Lactobacillus was dominant among bacteria, and Saccharomyces was dominant among fungi. A correlation analysis showed that there were positive correlations between moisture, acidity, cellulose, lipase activities and Lactobacillus, and there were positive correlations between moisture content, acidity, cellulase activity, acidic protease activity and Saccharomyces. A total of 46 volatile flavor compounds were detected, of which 6 alcohols and 14 esters constituted the major portion, and 9 key flavor compounds with an ROAV > 1 were identified throughout the fermentation process. Isoamyl acetate had the highest ROAV and made the greatest contribution to the flavor.

Discrimination and characterization of volatile organic compounds and nutritional values of three varieties of chopped pepper seeds.

Fermented-chopped pepper is a widely consumed condiment in China due to its attractive flavor. Chopped pepper seed (CPS) is the byproduct generated during the production of chopped pepper and is generally discarded as waste. In this study, the volatile organic compounds (VOCs) and nutritional value of three varieties of CPS were investigated. Results indicated that the nutritional compositions of the three CPS varieties exhibited significant differences. All CPS samples contained 17 amino acids and were rich in fatty acids, with unsaturated fatty acids being predominant and accounting for 79 % of the total fatty acids. A total of 53 VOCs were identified by gas chromatography-ion mobility spectrometry, which could be classified into 9 groups, with aldehydes, esters, and alcohols comprising the three largest groups. The three varieties of CPS had remarkably varied aromas whereas there are five key VOCs (i.e., 2-pentylfuran, methional, ethyl 3-methylbutanoate, dimethyl disulfide, and nonanal) in all CPS samples. Network correlation analysis revealed that VOCs are closely correlated with amino and fatty acids. Thus, this study provides a useful basis for understanding the nutritional values and flavor characteristics of different CPS varieties, which could be used as an ingredient and might have great potential in the food industry.

GC-MS Coupled with Rate-All-That-Apply (RATA) to Analyse the Volatile Flavor Substances of Yellow Wine during Fermentation.

Yellow glutinous rice wine is a traditional Chinese beverage created by soaking, boiling, and fermenting glutinous rice. The majority of current studies on the flavor of yellow glutinous rice wine are based on instrumental analysis, with sensory analysis being overlooked. In this study, 36 volatile chemicals in the fermentation process of yellow wine were annotated by GC-MS and then an OPLS-DA model was built to screen out 13 distinctive substances (VIP > 1, p < 0.01). The relative odor activity value (ROAV) was calculated using the threshold values of these chemicals and 10 substances, including alcohols, esters, and aldehydes, were found as key contributors to the overall flavor of yellow wine. Following that, consumers quantified the sensory descriptors of yellow wine using rate-all-that-apply (RATA), and correspondence analysis revealed three groups of characteristic flavors and odors. Alcohols and esters were found to be key producers of flowery and fruity scents in yellow wine, according to correlation analysis. We discovered two alcohols that are rarely found in yellow wine: [R,R]-2,3-butanediol and 1-phenylethanol. The former was found to be favorably connected with wine scent and pungent odor, and its specific effect on flavor should be researched further.

Pasteurized Akkermansia muciniphila Reduces Fat Accumulation via nhr-49-Mediated Nuclear Hormone Signaling Pathway in Caenorhabditis elegans.

Pasteurized Akkermansia muciniphila (p-AKK) is related to lipid metabolism and helps control obesity. The main goal of this study was to investigate the role and mechanism of p-AKK in lipid metabolism using Caenorhabditis elegans. The results showed that p-AKK increased the healthy lifespan of nematodes and helped maintain exercise ability in aging, suggesting a potential increase in energy expenditure. The overall fat deposition and triglyceride level were significantly decreased and the p-AKK anti-oxidative stress helped to regulate fatty acid composition. Additionally, the transcriptome results showed that p-AKK increased the expression of lipo-hydrolase and fatty acid ß-oxidation-related genes, including lipl-4, nhr-49, acs-2 and acdh-8, while it decreased the expression of fat synthesis-related genes, including fat-7, elo-2 and men-1. These results partially explain the mechanisms underlying the fact that p-AKK decreases fat accumulation of C. elegans via nhr-49/acs-2-mediated signaling involved in fatty acid ß-oxidation and synthesis.

Antioxidant Activity of Vitis davidii Foex Seed and Its Effects on Gut Microbiota during Colonic Fermentation after In Vitro Simulated Digestion.

Vitis davidii Foex whole seed (VWS) is a by-product during the processing of grape products, which is rich in bioactive compounds that have great potential in the food industry. In this study, the bioactive compounds and antioxidant activity of VWS were determined, and their dynamic changes during in vitro colonic fermentation were also investigated after VWS subjected to in vitro simulated digestion. Results showed that VWS were rich in polyphenols (23.67 ± 0.52 mg GAE/g), flavonoids (13.13 ± 1.22 mg RE/g), and proanthocyanidins (8.36 ± 0.14 mg CE/g). It also had good DPPH and ABTS radical scavenging activity, which reached 82.10% and 76.10% at 1000 µg/mL. The alteration trend of the antioxidant activity during in vitro fermentation for 24 h was consistent with that of the content of bioactive substances, such as polyphenols, with the extension of fermentation time. The bioactive compounds and antioxidant activity showed a trend of increasing and then decreasing, reaching the highest value at 8 h. The high-throughput sequencing analysis of the regulatory effect of VWS on intestinal micro-organisms revealed that VWS influenced intestinal microbiota diversity. The relative abundance of beneficial microbiota, such as Blautia and Parabacteroides, increased by 4.1- and 1.65-fold after 24 h of fermentation compared with that of the control group. It also reduced Escherichia-Shigella by 11.23% and effectively reduced host inflammation, while increasing the contents of acetic acid, propionic acid, and other metabolites. Taken together, these results reveal the value of VWS utilization and provide new insights into the nutritional and microbiota modulation effects of VWS, which could therefore serve as a nutraceutical ingredient in health promotion.

UPLC-QQQ-MS/MS-based widely targeted metabolomic analysis reveals the effect of solid-state fermentation with Eurotium cristatum on the dynamic changes in the metabolite profile of dark tea.

Eurotium cristatum is the predominant fungus and key contributor to the characteristics of post-fermented Fu brick tea (FBT) during manufacturing. In this study, the influence of solid-state fermentation (SSF) with E. cristatum on the chemical profile dynamic changes of dark tea was investigated. Results indicated that total phenolics, flavonoids, theaflavins, thearubigins, and galloyl catechins consistently decreased, degalloyl catechins and gallic acid increased in the initial stage of fermentation and decreased after long-term fermentation, and theabrownins continually increased. UPLC-QQQ-MS/MS-based widely targeted metabolomic analysis revealed that the metabolites of dark tea processed by SSF with E. cristatum were drastically different from the raw material. A total of 574 differential metabolites covering 11 subclasses were detected in the whole SSF of dark tea, and the most drastic changes occurred in the middle stage. Phenolic acids and flavonoids were the two major classes of differential metabolites. A series of reactions such as degradation, glycosylation, deglycosylation, methylation, and oxidative polymerization occurred during SSF. Overall, SSF with E. cristatum greatly influenced the metabolites of dark tea, which provided valuable insights that E. cristatum is critical in forming the chemical constituents of FBT.

Analysis of oral microorganism diversity in healthy individuals before and after chewing areca nuts using PCR-denatured gradient gel electrophoresis.

To analyze oral microbial diversity in the saliva of 8 healthy individuals before and after chewing areca nuts. Saliva samples were collected before chewing areca nuts, after chewing areca nuts for 5 min and after chewing areca nuts for 30 min. DNA was extracted, and microbial diversity was examined using PCR-denaturing gradient gel electrophoresis (PCR-DGGE). When examining DGGE profiles collectively, the bands associated with Streptococcus and Veillonella were the most intense, making them the most prevalent bacteria. Furthermore, the band intensities did not decrease after chewing areca nuts for 5 or 30 min; thus, these bacteria were unaffected. However, when examining some individuals, the band intensities for Streptococcus and Veillonella became more intense after 5 min of chewing and then returned to the pre-chewing level. This difference may be attributed to the mechanical movements of the oral cavity or individual differences. Other bacteria, such as Neisseria, Actinomycetes, and Rothia dentocariosa, were also found to have an increased or decreased prevalence following areca nut-chewing. Since the predominant species that are present following areca nut-chewing include Streptococcus and Veillonella, it would seem likely that these bacteria play an important role in the periodontal diseases associated with areca chewing.

Proteomic changes in EHEC O157:H7 under catechin intervention.

Catechin exhibits antimicrobial activity against various microorganisms, such as EHEC O157:H7. This study reports the bactericidal effect of catechin on EHEC O157:H7 in simulated human gastrointestinal environment and the underlying antibacterial mechanism. Bacteriostasis test results showed that the minimum bactericidal concentration of catechin for EHEC O157:H7 was 5 g/L. The bactericidal effect of catechin in the gastrointestinal juice became more significant with increased culture time, and catechin exhibited a synergistic effect with bile salt in inhibiting EHEC O157:H7. Changes in the profile of protein expression in EHEC O157:H7 in response to catechin intervention were investigated. Two-dimensional electrophoresis identified 34 proteins with significantly altered expression. A total of 2 and 12 proteins were upregulated and downregulated, respectively. However, 20 proteins disappeared. No new protein was expressed compared with the control. Hence, catechin intervention resulted in diverse changes in the expression of proteins associated with cell structure and genetic information processing. Catechin could cause the disappearance of certain proteins or the destruction of certain peptides. These processes lead to the inhibition of EHEC O157: H7 cells.