Search Results (762)

Interest in using Tibetan tea for fermented food production has increased due to its bioactive components and distinctive flavor characteristics. However, its application in Daqu prepared with Tibetan tea remains limited. This study investigated the effects of Tibetan tea addition on Daqu fermentation and Baijiu flavor formation using integrated microbiome and metabolome approaches. High-throughput sequencing, GC-MS, free amino acid analysis, electronic sensory analysis, and correlation network analysis were performed to characterize microbial and metabolic changes. Compared with wheat Daqu (WD), Tibetan tea Daqu (TD) showed higher microbial richness and enhanced fermentation performance (p < 0.05), with enrichment of functional microorganisms including Sphingobium, Komagataella, and Cyberlindnera, which were associated with enzyme activities and flavor precursor formation. Tibetan tea Daqu Baijiu (TDB) exhibited distinct metabolic profiles, with increased levels of esters, acids, terpenes, and free amino acids, contributing to a flavor profile characterized by ester aroma with sweet, umami, woody, and tea aroma characteristics. Correlation analysis revealed that Tibetan tea-driven microbial restructuring was linked to phenylalanine metabolism, esterification, and phenolic transformation pathways. These findings link raw materials, microbiota, and flavor formation, providing a basis for targeted Baijiu design. Full article

Physalis pubescens L. is a seasonal fruit with high nutritional value but a short shelf life that limits its processing and utilization. This study integrated metagenomics and metabolomics to investigate the comparative effects of Lactiplantibacillus plantarum fermentation on volatile flavor metabolites and microbial community composition of P. pubescens by comparing initial (0 h) and post-fermentation (24 h) states. After 24 h of fermentation, 1316 volatile compounds were putatively identified by GC-MS, with 592 metabolites significantly changed and 501 upregulated and 91 downregulated. Key flavor compounds that impart citrus, floral, fruity, and rose notes including D-limonene, geraniol, D-carvone, and phenylethyl alcohol were markedly increased. Metagenomic analysis revealed that L. plantarum rapidly dominated the microbial community (relative abundance surged from <0.05% to ~72%) while effectively suppressing potential spoilage bacteria such as Escherichia coli. Functional gene annotation demonstrated significant enrichment of amino acid, carbohydrate, and fatty acid metabolism pathways, with key enzyme genes (L-lactate dehydrogenase, pyruvate oxidase, acetyl-CoA carboxylase) predominantly assigned to L. plantarum, suggesting their potential contribution to the generation of organic acids, ethanol, and esters. Spearman correlation analysis indicated that Lactobacillaceae genera were significantly positively correlated with terpenoids, phenols, alcohols, and aldehydes. This study provides the first metagenomics-metabolomics insight into the microbial and molecular mechanisms associated with flavor formation in LAB-fermented P. pubescens, offering a theoretical foundation for developing stable and controllable fermented fruit products. Full article

Postharvest quality deterioration of Korla fragrant pear (Pyrus sinkiangensis Yu) severely constrains its market value, yet the regulatory role of preharvest soil management in shaping postharvest performance remains poorly understood. Although green manure is widely adopted to ameliorate orchard soil degradation, species-specific modulation of postharvest storage trajectories and the quantitative fidelity of soil-to-fruit nutrient transmission have rarely been resolved for climacteric pear species. This study investigated how green manure species modulate fruit quality at harvest and during postharvest storage life and their underlying soil–fruit linkages. Three preharvest treatments were imposed, as follows: control (CK), sweet clover (CM), and alfalfa (MX). Fruits were harvested and stored at 4 °C, with samplings at 1, 5, 10, 15, and 20 d. A critical quality transition was identified at 15 d, characterized by the concurrent peaking of soluble sugars, organic acids, vitamin C, and anthocyanins alongside an optimal sugar–acid ratio. Beyond this inflection point, CM and MX diverged markedly: CM enhanced soluble sugar accumulation, anthocyanin retention, and ester volatile production—most notably hexyl acetate, which increased over 14.4-fold—thereby generating a pronounced fruity aroma bouquet. Conversely, MX sustained higher amino acid and vitamin C levels and conferred superior late-storage stability, evidenced by a three-fold lower coefficient of variation in the sugar–acid ratio relative to CK. Partial-least-squares structural equation modeling (PLS–SEM) revealed soil fertility as the principal exploratory associative factor of fruit quality, but the fidelity of soil-to-fruit transmission was species-dependent. MX exhibited the highest observed associative strength (R² = 0.971), whereas CM exhibited attenuated transmission fidelity (R² = 0.777), with network analysis further indicating that CM exhibited divergent associative patterns of key soil–fruit correlations. These findings suggest that green manure identity is linked to postharvest quality through divergent soil–fruit coupling pathways: alfalfa shows nutrient transmission efficiency and stabilizes nutritional quality, whereas sweet clover promotes sugar-aroma accumulation at the cost of reduced soil–fruit conversion fidelity. Species-specific green manure selection thus offers a viable strategy for targeted modulation of postharvest traits in Korla fragrant pear. Full article

Pixian Doubanjiang (PXDB) is a traditional Chinese fermented condiment whose characteristic aroma and taste are strongly influenced by fermentation conditions. This study aimed to systematically compare the flavor profiles of PXDB produced via traditional open fermentation (TOF) and industrial closed fermentation (ICF), aiming to elucidate the chemical basis of sensory divergence and provide scientific support for industrial process optimization. In this study, PXDB samples were evaluated using sensory evaluation, GC-IMS, ¹H-NMR metabolomics, and multivariate statistical analysis. Sensory evaluation revealed that ICF exhibited a stronger soy sauce-like aroma, alcohol note, and umami intensity, whereas TOF and ICF showed comparable sweetness, sourness, chili-like aroma, and roasted aroma. GC-IMS putatively identified 126 volatile compounds, and multivariate analyses demonstrated a clear separation between the two fermentation modes. Based on combined criteria of VIP > 1, FDR-adjusted p < 0.05, and |fold change| > 2, 35 differential volatile compounds were identified. ICF was characterized by higher levels of esters, particularly ethyl esters, and selected ketones, while TOF showed enrichment of higher alcohols, terpenes, and sulfur compounds. ¹H-NMR analysis identified 54 non-volatile metabolites, of which 16 differed significantly between TOF and ICF, mainly involving amino acids, organic acids, and carbohydrates. Pathway analysis highlighted branched-chain amino acid and glutamate-related metabolism as key contributors to flavor divergence. Correlation analysis further revealed that soy sauce-like aroma and umami perception were strongly associated with amino acid-derived metabolites, esters, sulfur-containing compounds, and branched-chain aldehydes, highlighting the coordinated contribution of volatile and non-volatile compounds to flavor differentiation. Overall, fermentation mode was found to reshape PXDB flavor through coordinated modulation of volatile and non-volatile metabolism, providing experimental insight for improving industrial fermentation quality. Full article

Phenylglycine (Phg) is a nonproteinogenic α-amino acid found in various bioactive molecules. The C-terminal activation of N-acyl Phg is often accompanied by oxazolone-mediated racemization, arising from the direct attachment of the phenyl ring to the α-carbon. After peptide bond formation with another chiral amino acid, this stereochemical erosion is observed as Phg-site epimerization and diastereomer formation. N-acyl activated esters, particularly N-hydroxysuccinimide (OSu) esters, are widely used for peptide bond formation with proteinogenic α-amino acids. Our previous study on N-trifluoroacetyl phenylglycine (TFA-Phg-OH) revealed that Phg-site epimer formation could still occur when TFA-Phg-OSu was employed as an acyl donor for coupling with amino acid ester hydrochlorides (AA–OMe·HCl) in the presence of a soluble organic base. To address these issues, in this study, we report a base-limited one-pot coupling of TFA-Phg-OH with α-amino acid ester hydrochlorides (AA–OR·HCl; R = Me or tert-Bu) using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (WSCD·HCl), which effectively suppresses Phg epimerization. The resulting TFA-Phg–AA–OR dipeptides (AA = Ala, Val, Leu, Met, Phg) were all obtained at a >60% yield with a diastereomeric excess (de) ≥ 98.5%. Notably, reducing the amount of triethylamine further minimized epimer formation, while Ba(OH)₂·8H₂O and trifluoroacetic acid enabled stereoretentive deprotection of the N-TFA group and tert-butyl ester, respectively. This workflow provides practical access to both protected and deprotected Phg–AA motifs, thereby facilitating the preparation of unprotected Phg-containing peptide building blocks. Full article

Hawthorn (Crataegus pinnatifida) pulp is characterized by high levels of organic acids and polyphenols, yet its strong acidity limits sensory acceptance. In this study, Streptococcus thermophilus 540, Lactobacillus brevis 647, and their mixed culture (1:1) were applied to ferment hawthorn pulp. Changes in organic acids, individual phenolics, free amino acids, volatile compounds, antioxidant capacity, and global metabolic profiles were systematically investigated using targeted analysis combined with untargeted metabolomics. Fermentation markedly reshaped the metabolic composition of hawthorn pulp, with mixed fermentation exhibiting the most pronounced metabolic reprogramming. Co-fermentation significantly enhanced phenolic derivatives and aromatic amino acid-related metabolites, while promoting a more balanced distribution of organic acids and esters, contributing to improved antioxidant potential and flavor coordination. Multivariate analyses confirmed that mixed fermentation formed a distinct metabolic pattern rather than a simple additive effect of single strains, characterized by expanded metabolic diversity and pathway complementarity. These findings provide mechanistic insight into strain-dependent and synergistic metabolic modulation during fruit fermentation and support mixed lactic acid bacteria fermentation as a promising strategy for improving the functional and sensory quality of hawthorn-based products. Full article

This study examined the effects of soy sauce-based marinades containing fruit extracts (pineapple, apple) and sugar on the physicochemical, amino acid, flavor, and sensory characteristics of pork bulgogi. Five marinades (sugar only, pineapple, apple, pineapple+sugar, apple+sugar (App+Sug)) were compared. Pineapple exhibited high sweetness, acidity, and protease activity, consequently enhancing essential amino acids but causing undesirable mushy texture due to excessive proteolysis. Meanwhile, apple enriched umami-related amino acids (Glu, Gln) and provided balanced organic acid and sugar profiles without structural degradation. HPLC confirmed pineapple was rich in sucrose and citric acid, while apple contained more fructose and malic acid. Fruit-containing marinades increased esters, alcohols, and Maillard compounds, while reducing lipid oxidation aldehydes, thereby contributing to improved aroma and oxidative stability. Sensory evaluation revealed App+Sug marinade achieved the highest scores in flavor, tenderness, chewiness, and overall preference, thus indicating synergistic effects of fruit acids and sugars. Conversely, pineapple-based marinades, despite strong tenderizing potential, were less palatable. Overall, App+Sug marinade provided the best balance of flavor, tenderness, and consumer acceptability, while pineapple requires controlled application to prevent excessive softening. Full article

Whisky is well-known worldwide owing to its unique flavor, and its fermentation and distillation conditions have a significant effect on its aroma. In this paper, new-make spirits were prepared by four fermentation conditions (two distilling yeasts and two fermentation temperatures), and the different stages (wort, wash, low wine, and new-make spirit) of the samples were collected. The main aroma compounds and their precursors were initially determined in wort and wash samples by GC-MS, UPLC-MS and HPLC. Results showed that Strecker degradation, reduction, and esterification occurred during the fermentation process, leading to decreased contents of amino acids and increased contents of volatile esters, alcohols, and acids. Moreover, the two distilling yeasts exhibited their respective optimal fermentation temperatures. Then, the distillation process was evaluated by two-dimensional gas chromatography–olfactory–mass spectrometry (GC×GC-O-MS), and 74 aroma compounds were found in different stages of new-make whiskies fermented by the two distilling yeasts and one brewer’s yeast. The contents of most compounds were enhanced by at least ten times after two distillations, while the contents of some sulfur compounds decreased. Finally, the feature aroma-active compounds of each new-make whisky were identified according to rOAV. These results provided theoretical and methodological support for yeast selection and process control in whisky production. Full article

Daqu is a key starter used in Baijiu production, and its microbial composition and associated metabolic functions play critical roles in fermentation performance and flavor development. This work aimed to reveal how Daqu-making temperature regulates microbial community divergence and subsequent metabolite formation via multi-omics analysis so as to provide theoretical guidance for Daqu quality control. In this study, physicochemical analysis, metagenomic sequencing, and metabolomic profiling were combined to investigate the microbial community structure, functional differentiation, and metabolite characteristics of nine Daqu samples collected from six major Baijiu-producing regions in China. The temperature during Daqu preparation was found to be a primary factor driving microbial community assembly and functional specialization. Medium-temperature Daqu exhibited higher saccharifying activity (up to 867 U) and greater microbial diversity with the enrichment of amino acid metabolism-related pathways, indicating enhanced protein degradation and amino acid utilization for the formation of flavor precursors. In contrast, high-temperature Daqu showed stronger capacities for carbohydrate degradation and conversion, particularly in starch and sucrose metabolism, which were closely associated with the enrichment of thermotolerant fungi and bacteria. LEfSe analysis identified 47 distinct microbial biomarkers (LDA score > 3.0), which could differentiate between medium- and high-temperature Daqu. Redundancy analysis indicated that environmental factors (moisture and acidity) together with functional properties (fermentation, esterification, liquefaction, and saccharification) act as key drivers of microbial functional patterns. Metabolomic analysis further revealed that medium-temperature Daqu had higher abundances of esters and fatty acids, whereas high-temperature Daqu had higher proportions of alcohols and ketones. Taken together, these results provide a multi-omics perspective on temperature-driven microbial functional differentiation in Daqu and offer a scientific basis for quality-oriented regulation and process optimization in Baijiu production. Full article

Traditional fermented foods harbor diverse microbial resources and provide an important reservoir for fermentation applications. We compared selected fermentation-related metabolite profiles of yeast strains isolated from traditional Korean fermentation starters and fermented foods, including nuruk and makgeolli. A total of 63 Saccharomyces cerevisiae strains and 23 non-Saccharomyces strains were cultured in YPD medium for 24 h, and volatile compounds, organic acids, and free amino acid-related compounds were analyzed. Non-Saccharomyces strains generally showed higher levels of ester compounds, whereas S. cerevisiae strains exhibited relatively higher levels of alcohol compounds. In particular, Kluyveromyces marxianus KJ-L showed high levels of both ester and alcohol-related volatile compounds, suggesting its potential as a candidate strain for further aroma-related evaluation. Organic acid and free amino-related profiles also differed between the two yeast groups. These results highlight the distinct metabolic traits of S. cerevisiae and non-Saccharomyces strains and provide useful screening information for selecting candidate microbial resources for further validation in fermented food systems. Full article

This study evaluated how a lemon essential oil–rutin–chitosan coating (CS-LEO/NE-R), prepared from a 5:95 (v/v) lemon essential oil/rutin-containing nanoemulsion and a chitosan solution containing 1.5% chitosan, 1% acetic acid, and 5% glycerol, combined with controlled freezing-point storage preserves seasoned white snakehead fillets. Compared with controlled freezing-point storage alone, the combined treatment significantly inhibited oxidation, volatile nitrogen accumulation, texture softening, and microbial growth. On Day 10, the coating group recorded a total viable count of 4.98 log CFU/g, which was below the national limit (5 log CFU/g), whereas the control group went beyond this limit by Day 7. This extended the microbiological and physicochemical acceptability period by approximately 3 days under the present experimental conditions. Untargeted metabolomics revealed 2267 metabolites, and the differentially abundant ones mainly comprised amino acids, heterocyclic compounds, aldehydes, ketones, and esters. KEGG enrichment suggested that changes in linoleic acid metabolism, terpenoid related annotations, the actin cytoskeleton, and the phospholipase D signaling pathway were associated with delayed quality deterioration. This work provides a theoretical basis for the composite biopreservation of aquatic products. Full article

Synthesis of bifunctional cytisine–squaramide derivatives bearing a single amino acid moiety has revealed an unexpected and intriguing chemical challenge. During modification of cytisine squaramates with α-amino acids, base-sensitive amido esters readily underwent hydrolysis, forming poorly soluble amido-acid side products that resisted standard purification and initially obscured their identity. Persistent observation of these elusive precipitates prompted a deliberate co-crystallization approach, which unambiguously revealed their supramolecular nature using single-crystal X-ray diffraction. With this insight, optimized purification strategies allowed isolation of analytically pure Cyt-SQ-OH and its derivatives, which were characterized by complementary spectroscopic techniques, X-ray crystallography and computational studies. Furthermore, the DFT-optimized parameters of all compounds were determined, providing additional insight into their structural and electronic properties. This work highlights the interplay between reactivity, solubility, and supramolecular assembly in cytisine–squaramide-amino acid hybrids, providing a robust platform for future exploration of multifunctional conjugates with potential applications in medicinal chemistry, molecular recognition, and materials science. Full article

The flavor profile of Longmen rice vinegar directly influences consumer purchase intention, and understanding its variation during fermentation is crucial for final product quality control. In this study, the flavor dynamics during the fermentation of Longmen rice vinegar were systematically investigated. Sensory evaluation indicated that acidity increased significantly during the acetic acid fermentation stage, while alcoholic and fermented odors decreased continuously. Instrumental analysis identified 129 volatile compounds, predominantly esters, alcohols, and acids. Based on relative odor activity value (r-OAV) analysis, acetic acid, 3-methylbutyl acetate, 2,3-butanedione, benzeneacetaldehyde, phenethyl alcohol, ethyl acetate, 2-phenylethyl acetate, ethyl 4-methyl-pentanoate, 3-methyl-1-butanol, and 3-methylbutanal were determined to be the major contributors to the overall aroma. Orthogonal partial least-squares discriminant analysis (OPLS-DA) further screened 21 key differential compounds. Significant variations in organic acid and amino acid contents during fermentation were also observed. Correlation analysis revealed relationships between key aroma compounds and organic, as well as amino, acids. These findings establish a foundation for monitoring flavor dynamics during the fermentation of Longmen rice vinegar. Full article

Messenger RNA (mRNA) therapeutics are redefining treatment approaches in vaccines, cancer immunotherapy, protein replacement, and gene editing. Lipid nanoparticles have enabled early clinical successes, but they can be limited by liver-dominant biodistribution, long-term storage stability, and systemic tolerability. Polymeric delivery systems offer a versatile alternative, with tunable physicochemical properties enabling precise control over mRNA complexation, protection, release, and targeting. This review examines recent progress across polyethyleneimine derivatives, poly(β-amino ester)s, poly(amino acid)s, polyesters, dendrimers, charge-altering releasable transporters, and lipid-polymer hybrids. We highlight strategies such as structural modification, stimuli-responsive designs, and high-throughput polymer screening that enhance stability, reduce cytotoxicity, and enable organ- or cell-specific delivery. Addressing challenges in immunogenicity, biodistribution, and manufacturing scalability will be pivotal to translating these innovations into safe and effective mRNA therapeutics. Full article

Fertilizer management plays a critical role in regulating both yield and aroma quality in fragrant rice. However, the combined effects of functional fertilizers on these traits across different varieties and ecological conditions remain poorly understood. In this study, field experiments were conducted at two sites (Fumin and Dali) using two japonica fragrant rice varieties (Yunjing 37 and Liuxiangzi 1) under four fertilization treatments: T1 (conventional fertilization); T2 (compound fertilizer + silicon fertilizer); T3 (compound fertilizer + magnesium ammonium phosphate + amino acid-chelated calcium); and T4 (compound fertilizer + bio-organic fertilizer + zinc + amino acid water-soluble fertilizer). Compared with T1, silicon application (T2) significantly increased grain yield by 8.58–15.08%, primarily through synergistic increases in effective panicles and grains per panicle. Treatments T3 and T4 significantly enhanced grain 2-acetyl-1-pyrroline (2-AP) content by 18.32–32.67% and increased the diversity of volatile compounds. Correlation analysis revealed that 2-AP content was positively correlated with ketones (r = 0.373, p < 0.05) and alcohols (r = 0.363, p < 0.05), and negatively correlated with aldehydes and esters. Multifactor ANOVA showed no significant variety × treatment interaction for yield or 2-AP content (p > 0.05), indicating consistent responses across varieties. These results provide preliminary evidence that silicon fertilizer serves as an effective strategy for yield improvement, while combined application of calcium, magnesium, and amino acids enhances aroma quality by promoting the accumulation of 2-APm ketones, and alcohols. However, because treatments T3 and T4 contained multiple components, the individual contributions of Ca, Mg, or amino acids cannot be isolated. Multi-year trials are required to confirm the stability of these effects, featuring a differentiated fertilization strategy—silicon for yield and medium/trace elements for aroma—applicable across varieties, with site-specific variety selection further optimizing performance. Full article