Physicochemical and molecular transformation of novel functional peptides from Baijiu

Identification of Chinese baijiu from the same brand based on a graphene quantum dots fluorescence sensing array

The identification of Chinese baijiu is crucial to regulating the international market and maintaining legitimate rights, as the popularity, influence and awareness of baijiu are growing. A graphene quantum dot (GQD) based fluorescence sensor array is designed in this paper. Upon using only GQDs as a single sensing element, combining three different solvents improves the sensing array's detection sensitivity while simplifying material preparation and experimental detection. Adding organic substances creates intermolecular forces between the GQDs and the solvent, causing the fluorescence intensity to change. The sensor array was able to distinguish 21 types of organic matter, different ratios of quaternary mixed organic materials and 17 types of baijiu of the same brand. It also showed excellent performance in the detection of species in blind samples, with the machine learning algorithm successfully distinguishing baijiu from five other distilled spirits. The experiment provides guidance for the practical application of GQDs and provides a simple but effective reference for sensor arrays to detect baijiu.

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.

Goat milk-derived short chain peptides: Peptide LPYV as species-specific characteristic and their versatility bioactivities by MOF@Fe3O4@GO mesoporous magnetic-based peptidomics

Goat milk as an ideal substitute for human milk has not been sufficiently explored. An in-situ synthesized MOF@Fe₃O₄@GO was demonstrated as a magnetic mesoporous adsorbent for efficiently enriching short chain peptides (SCPs) in milk compared with the routine solid phase extraction approach with graphite carbon black or C₁₈ as the packing material in terms of the number of enriched SCPs and data stability. A total of 61 and 126 SCPs were identified and quantified in bovine milk (0.09-89.34 μg L^-1) and goat milk (10.5-1267.06 μg L^-1), respectively, and peptide LPYV can be used as a potential marker for adulteration of goat milk. Relative high expression of chymotrypsin and pepsin by EnzymePredictor analysis could partially elaborate the reason of the abundance of SCPs in goat milk. Compared with bovine milk, further bioinformatics analysis indicated that goat milk could own higher nutritional value because of relative higher concentrations (>1 mg/L) of SCPs (LLV, FL, LVYP) with confirmed bioactivities including angiotensin-converting enzyme (ACE) inhibitor, antioxidant, dipeptidylpeptidase (DPP) III and DPP IV inhibitor, etc. Overall, this study opened a novel avenue for understanding versatility benefit of dairy products from a perspective of SCPs by using a developed MOF@Fe₃O₄@GO mesoporous magnetic-based peptidomics.

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.

Novel insight into the transformation of peptides and potential benefits in brown fermented goat milk by mesoporous magnetic dispersive solid phase extraction-based peptidomics

Brown fermented goat milk as an excellent source of bioactive peptides has only been partially elucidated. Meticulously synthesized MOF@MG as magnetic sorbent for enriching endogenous peptides owned higher reproducibility and uniform distribution of peptides PI compared with ultrafiltration. Combined with UHPLC-Q-Orbitrap, fermentation for 12 h in brown goat milk with the highest overall acceptable degree through sensory evaluation was utilized to explore the transformation of peptides and health benefits, with trypsin or plasmin hydrolyzing proteins and aminopeptidase or carboxypeptidase hydrolyzing peptides to small peptides or amino acids. A total of 1317 peptides were identified by database matching (1259) and de novo sequencing (58), among 18 peptides could originate from gene-independent enzymatic formation and top 25 characteristic peptides were quantified with concentration ranging from 0.12 to 6.40 mg L^-1. Bioinformatic analysis results indicated that brown fermented goat milk possesses higher health benefits because of more than 50 peptides with potential bioactivity.

Strategies for studying in vivo biochemical formation pathways and multilevel distributions of sulfanilamide metabolites in food (2012-2022)

Sulfonamide metabolites are a major source of food pollution worldwide. However, the formation of internal sulfanilamide metabolites has only been investigated for selected compounds. In this paper, the fragmentation mechanism and characteristic ions of sulfonamide metabolites are reviewed using density functional theory and Q-Orbitrap high-resolution mass spectrometry. The result of the protonation site, rearrangement and bond breaking induced fragmentations at C₆H₆NO₂S⁺m/z 156.01138, C₆H₆NO⁺m/z 108.04439, and C₆H₆N⁺m/z 92.04948. Mass shifts are calculated for derivative metabolites, including hydrogenation, acetylation, oxidation, glucosylation, glucosidation, sulfation, deamination, formylation, desulfonation and O-aminomethylation. Given their homologous series, it is demonstrated that similar metabolic reactions occur for all sulfonamides. The suspicious sulfonamide metabolites are confirmed by d-labelling experiments and reference standards. This is the first review of the latest advances in the field of sulfonamide metabolite prediction (2012-2022), and scheme design for metabolite multirresidue screening, as well as the challenges in the mass spectrometry evolution.

Bioaccessibility of phospholipids in homogenized goat milk: Lipid digestion ecology through INFOGEST model

Phospholipids-rich goat milk provides health benefits to consumers. The effects of homogenization on the disruption and recombination of milk fat globule membrane and change the fatty acid positional distribution in glycerophospholipids profile by phosphatidylcholine metabolism pathways were investigated. Goat milk was homogenized at different intensity pressure. Homogenized samples were introduced into harmonized INFOGEST digestion model. Results showed that phosphatidylcholine increased significantly during storage in 30 MPa and were approximately twice that in raw milk (LOD 0.27-1.49 μg/L and LOQ 0.89-4.92 μg/L, respectively). Meanwhile, both linoleic acid (C18:2) and α-linolenic acid (C18:3ω-3), the foremost polyunsaturated acyl chains in homogenized milk extracts, showed upward trends. Notably, homogenization increased the number and altered the composition of Sn-1, 2 diacylglycerols via increasing trypsin and pancreatic lipase (PLRP2, MAUC15, CD36 and BSSL) expression and accelerated the phosphatidylcholine conversion. Ultimately, the relationship between homogenization and milk fat globule recombination and phospholipids bioaccessibility was preliminary established.

Effects of Short-Chain Peptides on the Flavor Profile of Baijiu by the Density Functional Theory: Peptidomics, Sensomics, Flavor Reconstitution, and Sensory Evaluation

The effect of peptides on the flavor profile of Baijiu is unclear as a result of their trace concentrations in the complex matrix, and therefore, the study involving the interaction mechanism between peptides and flavor compounds is limited. In this study, short-chain peptides (amino acid number between 2 and 4, SCPs) associated with the Feng-flavor Baijiu (FFB) were comprehensively analyzed by a dedicated workflow using ultra-high-performance liquid chromatography Q Orbitrap high-resolution mass spectrometry, flavor reconstitution experiments, sensory analysis, and density functional theory (DFT) analysis. The concentrations of 96 SCPs intimately related with six different grades of honey aroma intensity in FFB were quantified (0.12-155.01 μg L^-1) after multivariable analysis, Spearman's correlation analysis (ρ ≥ 0.7), and confirmation with synthetic standards, and 32 dominant odorants with an odor activity value of ≥1 in FFB with the highest intensity of honey aroma were quantified by gas chromatography-mass spectrometry and gas chromatography-flame ionization detection analyses. The results of flavor reconstitution experiments and sensory analysis indicated that the SCPs can obviously influence the honey aroma with amplifying the fruity, sweet, and flora flavor odor characters (p < 0.05) while significantly reducing the acidic character (p < 0.001), which could be attributed to the most stable complex structure between SCPs and odor-active compounds calculated by DFT being butanoic acid, followed by β-damascenone, 3-methylbutanal, and ethyl hexanoate, and the multiple sites as a hydrogen bond donor or acceptor in SCPs can form a stable ternary structure with water and ethanol inside the peptide chain or carboxyl terminal of SCPs, consequently improving the stability of the Baijiu system. The results highlighted the important role of SCPs on the volatiles in Baijiu and laid the foundation for further facilitating the sensory quality of Baijiu products.

Molecular mechanism of Mare Nectaris and magnetic field on the formation of ethyl carbamate during 19 years aging of Feng-flavor Baijiu

Ethyl carbamate (EC) is carcinogen occurring naturally in fermented foods, while the EC formation pattern in Feng-flavor Baijiu during Mare Nectaris storage and magnetic field treatment remains controversial. In this work, variation of EC in Mare Nectaris and magnetic field were investigated for the first time through ultra high performance liquid chromatography quadrupole-orbitrap high resolution mass spectrometry (UHPLC-Q-Orbitrap). Quantification results revealed that EC decreased significantly in the stage of 3-9 years and kept at 12.4 μg L-1 after 10 years of aging. Arginine succinate synthase (ASS) and urease were deemed as vital factors for EC decomposition. Degradation effetc of EC in 250 mT is simillar to that of EC in Baijiu stored in Mare Nectaris for 8 years. This is due to that aging process was accelerated by magnetic field and the content of total acid in Baijiu was increased, creating a favorable environment for decomposition of EC and urea.

Hydrogen bonds and hydrophobicity with mucin and α-amylase induced honey aroma in Feng-flavor Baijiu during 16 years aging

Honey aroma is one of the most significant factors of Feng-flavor Baijiu, which is also an essential element to attract consumers. However, the evaluation and chemical basis of honey aroma is unclear. Palmitoleic acid, lagochilin, phomotenone and ethyl behenate were confirmed to be the strongest contributors to honey aroma by time-intensity analysis and UHPLC-Q-Orbitrap-MS. Predictive modeling was developed for processing honey aroma intensity responses in order to obtain significant Feng-flavor Baijiu rankings. In this study, the effects of ex-vivo saliva on Feng-flavor Baijiu were investigated for the first time. Mucin and α-amylase, as major proteins in ex-vivo saliva, were applied to simulate molecular docking of ethyl benzoate. Mucin and α-amylase modified the aroma release, which depended on hydrogen bonds and hydrophobic interactions, respectively. It is blazing a trail in the field in sensory experience of Feng-flavor Baijiu as well as contributes to our understanding of Feng-flavor Baijiu drinking process.

Discovery of Se-containing flavone in Se-enriched green tea and the potential application value in the immune regulation

Selenium (Se)-enriched green tea has been recognized as a possible source of supplemental Se, while the structural and physiological activities of Se-containing flavone are still unclear. In this study, a Se-containing flavone was isolated from Se-enriched green tea by high-speed counter-current chromatography (HSCCC) and characterized through UHPLC-Q-Orbitrap, FT-IR and NMR. Results proved that HSeO₃^- can be combined with the alcohol hydroxyl of 2-phenylchromone in flavone and the content of Se-containing flavone in tea was 15690.4 μg L^-1. Additionally, Se-containing flavone can effectively inhibit the production of nitric oxide (NO), and downregulate expression of TNF-α and IL-6. Compared with regular flavone extracted from green tea (43.24 pg mL^-1), release of IL-10 was higher in Se-containing flavone group (53.37 pg mL^-1), indicating that Se-containing flavone played an important role in the process of severe inflammatory injury. The results indicated that Se-containing flavone was an attractive natural ingredient for developing novel functional foods.