Content changes of Jiupei tripeptide Tyr-Gly-Asp during simulated distillation process of baijiu and the potential in vivo antioxidant ability investigation

Virtual screening, identification, and potential antioxidant mechanism of novel bioactive peptides during aging by a short-chain peptidomics, quantitative structure-activity relationship analysis, and molecular docking

Antioxidant peptides have received a great deal of attention. However, only a few studies have been conducted on the antioxidant peptides originating from Baijiu. A total of 1490 features deemed potential short-chain peptides (the amino acid number between 2 and 4, SCPs) were screened and analyzed by a customized short-chain peptidomics approach in Feng-flavor Baijiu (FFB) during 14 years of aging, with an obvious discrepancy between FFB aged for 3 years and 6 years being observed. Thirty-nine characteristic SCPs in total were identified and accurately quantified by high-throughput parallel reaction monitoring-based synthetic standards, with the contents ranging from 0.16 to 279.33 μg L-1. Combined with the absorption, distribution, metabolism, excretion, and toxicity analysis model, PGRW, WK, SC, and PAW, four novel antioxidant peptides with high ABTS radical scavenging capacity, were obtained using a customized quantitative structure-activity relationship (QSAR) model based on a two terminal position numbering method, with satisfied coefficients of determination (R2), internal cross-validated R2 (Q2), and external R2 (R2pre) of 0.925, 0.808, and 0.665, respectively. Furthermore, these 4 antioxidant peptides could block the Keap-Nrf2 interaction and promote the accumulation of Nrf2 by molecular docking analysis, and the interaction energy between peptide PGRW and Keap1 was higher than that between epigallocatechin gallate and Keap1 based on CHARMm forced field. Overall, this study facilitated the discovery of functional peptides in Baijiu and the understanding of aging mechanisms.

Cross-modal interactions caused by nonvolatile compounds derived from fermentation, distillation and aging to harmonize flavor

Chinese liquor (Baijiu), unique liquor produced in China and among the six world-renowned distilled liquors, is never a follower of others. Flavor is the essential characteristics of Baijiu which largely affect consumers' acceptance and selection. Though the flavor of Baijiu has been widely explored, the majority of research and review mainly focused on the volatile compounds in Baijiu. The research status on detection, source and flavor contribution of nonvolatile compounds in Baijiu is clarified in the article based on available literatures and knowledge. The nonvolatile composition of Baijiu is the result of contributions of different degrees from each step involved in the production process. Gas chromatography-mass spectrometry combined with derivatization and ultra-high performance liquid chromatography coupled to mass spectrometry is the generally adopted methods for the characterization of nonvolatile compounds in Baijiu. Certain nonvolatile compounds are taste-active compounds. Cross-modal interactions caused by nonvolatile composition could affect the aroma intensity of flavor compounds in Baijiu. The work provides numerous incompletely explored but useful points for the flavor chemistry of Baijiu and lays a theoretical foundation for the better understanding of Baijiu flavor and rapid development of Baijiu industry.

Analysis of the Influence of Microbial Community Structure on Flavor Composition of Jiang-Flavor Liquor in Different Batches of Pre-Pit Fermented Grains

To explore the effects of microbial community changes on the key flavor substances in base Baijiu, this study analyzed the microbiome of the pre-pit fermentation grains using high-throughput sequencing technology and determined the flavor substances of the base Baijiu by GC-FID. The results showed the microbial community changed dynamically between the different rounds, as well as bacteria and fungi displayed different succession patterns. Next, the variations of skeletal flavor substances in the base Baijiu were analyzed by multiomics, and it was found that alcohols, acids, and esters were the most abundant, accounting for 88.16–98.87% of the total flavor substances, and decreased with the increase of the rounds. By calculating the Spearman coefficient, it was found that microorganisms such as Acinetobacter, Oceanobacillus, Saccharomyces, and Byssochlamys were significantly correlated with the n-Propano and 2,3-Butanediol and other components in the base Baijiu. Finally, 15 flavor substances such as Acetaldehyde, Propionaldehyde, and Isobutyraldehyde were identified as key substances by OAV analysis. This study is the first to reveal the potential association between the microbial community of pre-pit fermentation grains and flavor of base Baijiu and has the benefit of improving the quality of base Baijiu.

Unraveling variation on the profile aroma compounds of strong aroma type of Baijiu in different regions by molecular matrix analysis and olfactory analysis

Among 12 aroma types of Baijiu, the strong aroma type of Baijiu (Nongxiangxing Baijiu) is well received by customers for its rich and full aroma profile. According to the aroma characteristics of different geographical locations, Nongxiangxing Baijiu can be divided into Jianghuai, Sichuan and North categories. However, the reasons for the differences in Nongxiangxing Baijiu flavor in different regions are still unclear. Hence, representative brands (i.e., Gujinggong, Luzhou Laojiao and Banchengshaoguo) of Nongxiangxing Baijiu from three representative regions were chosen to explore their differences in profile aroma compounds. In this study, a total of 50, 41, 35 potential aroma compounds in Banchengshaoguo, Gujinggong, and Luzhou Laojiao samples were respectively identified by direct injection combined with gas chromatography-olfactometry/mass spectrometry (GC-O/MS). Among them, 18 aroma compounds were further recognized as important aroma compounds owing to their high flavor dilution (FD) value, Osme value, and odor activity value (OAV) ≥ 1. Moreover, the relationship between the above potential aroma compounds and the aroma profile of the three representative samples was analyzed by molecular matrix analysis. The results showed that various aroma compounds contributed differently to the flavor characteristics of Nongxiangxing Baijiu. In particular, 13 aroma compounds were tentatively defined as crucial profile aroma compounds due to their high aroma expression intensity and remarkable contribution to the flavor characteristics of Nongxiangxing Baijiu in different regions, and these crucial profile aroma compounds may be the reason for the difference in aroma profile of Nongxiangxing Baijiu from distinct regions.