Foods

Fresh fruit and vegetables remain metabolically active after harvest and are susceptible to chilling injury, senescence, and microbial decay, all of which can reduce quality and shorten their marketable life [...]

Lotus sprouts are a widely consumed aquatic vegetable, yet their quality remains poorly characterized. This study integrated physicochemical analysis, volatile flavor profiling, and metabolomics to evaluate quality differences among three lotus sprout cultivars, as well as different parts and grades. The apical portions had significantly higher contents of protein, total phenolics, and γ-aminobutyric acid than the stem portions. A total of 46 volatile compounds were identified by headspace solid-phase micro-extraction combined with gas chromatography–mass spectrophotometry (HS-SPME-GC-MS), and the abundance of 2,4-di-tert-butylphenol and 1-octen-3-ol was further confirmed using standards. Untargeted metabolomics identified 335 compounds, with sugars, polyphenols, and amino acids being the most abundant categories. Differentially accumulated metabolites between parts and cultivars were significantly enriched in glutathione metabolism, flavonoid biosynthesis, and amino acid metabolism. Notably, the two Baiyuzan cultivars generally accumulated higher levels of beneficial metabolites than Wuzhi No. 2, whereas the stem portion of the higher-grade Wuzhi No. 2 showed lower accumulation of sucrose and paprazine. Quantitative analysis of eight alkaloids using external standard calibration curves indicated that nuciferine was the most abundant alkaloid (13.3 to 31.1 μg/g). Collectively, this study provides a foundational framework for evaluating the metabolite profiles and application potential of lotus sprouts.

4-Alkyl branched-chain fatty acids (BCFAs), including 4-methyloctanoic acid (4-MOA), 4-ethyloctanoic acid (4-EOA), and 4-methylnonanoic acid (4-MNA), are important contributors to the characteristic odor of sheep meat. Their concentrations and composition are closely related to meat flavor quality and consumer acceptance. Understanding the mechanisms that regulate BCFA formation and accumulation is therefore important for improving sheep meat flavor. In this study, the concentrations of these three BCFAs were measured in muscle samples from Altay (ALT), Turpan (TLF), Inner Mongolian (NM), Tan, and Hu sheep. Untargeted muscle metabolomic data from ALT and TLF sheep were integrated with publicly available datasets, including metabolomic data from Tan sheep under different feeding conditions and transcriptomic and metabolomic data from Hu and Zang sheep. These datasets were used to investigate BCFA-related metabolic networks and candidate regulatory factors associated with ecological environment, nutritional conditions, and genetic background. The results show clear differences in BCFA accumulation among the sheep populations. All three BCFAs were below the limits of detection in ALT, TLF and NM sheep. Both 4-MOA and 4-EOA were detected in Tan sheep, whereas all three BCFAs were detected in Hu sheep. The concentrations of 4-MOA and 4-EOA in Hu sheep were approximately 14.4- and 12.5-fold higher than those in Tan sheep, respectively (p < 0.001). Multi-omics integration showed that BCFA-related metabolic variation was mainly associated with branched-chain amino acid metabolism, short-chain carbon metabolism, the tricarboxylic acid (TCA) cycle, and lipid metabolism. MMUT, ACAT1, and EHHADH were identified as candidate regulatory genes. These genes are involved in methylmalonyl-CoA conversion, acetyl-CoA/acetoacetyl-CoA metabolism, and fatty acid β-oxidation, respectively. Changes in energy demand, substrate utilization, and precursor availability may alter the partitioning of BCFA precursor carbon between central energy metabolism and lipid metabolism, thereby affecting BCFA formation and accumulation. In summary, MMUT, ACAT1, and EHHADH may influence the formation and accumulation of 4-MOA, 4-EOA, and 4-MNA by regulating key metabolic reactions and carbon partitioning between the TCA cycle and lipid metabolism. Ecological environment and dietary conditions may further contribute to this process by modifying energy metabolism and precursor substrate supply. These findings provide a theoretical basis for understanding BCFA-related flavor formation and for improving sheep meat flavor through genetic selection and nutritional regulation.