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In this study, six lipase-producing strains from food sources were screened for their ability to produce lipase. Among them, Staphylococcus epidermidis N30 and Yarrowia lipolytica C11 demonstrated high enzyme activities of 1.07 and 0.84 U/mL, respectively. They had the following enzymatic properties: optimum reaction temperature of 50 ℃ and pH of 8.0. The optimum substrate for S. epidermidis N30 was C4 ester, while that for Y. lipolytica C11 was C8 ester. The inoculation of sour meat with S. epidermidis N30 or Y. lipolytica C11 effectively enhanced the production of flavor substances, especially ethyl butyrate, ethyl caproate, ethyl caprylate, ethyl caprate, nonanal and 1-octen-3-ol, thus promoting the production of fruity, floral, wine-like, mushroom-like and fatty aromas in sour meat.

BACKGROUND: To date, cider production has primarily relied on Saccharomyces cerevisiae. Introducing novel non‐Saccharomyces yeasts can enhance the diversity of cider properties. Among these, the Metschnikowia genus stands out for its ability to produce hydrolytic enzymes that may impact the sensorial and technological properties of cider. This study focused on evaluating the impact of three Metschnikowia species – Metschnikowia koreensis (Mk), M. reukaufii (Mr), and M. pulcherrima (Mp) – which exhibit acid protease and esterase activity, on the quality enhancement of cider. RESULTS: The research findings indicate that the overall quality of cider produced through co‐fermentation with these species surpassed that of cider fermented with mono‐fermentation of S. cerevisiae (Sc). The cider fermented with the Sc + Mk combination exhibited the lowest levels of harsh‐tasting malic acid and higher levels of softer lactic acid. Sensory array analysis also demonstrated that the Sc + Mk fermented cider exhibited high sensor response values for compounds contributing to a complex overall olfactory composition and richness. Furthermore, the Sc + Mk fermented cider exhibited the highest total quantity and variety of volatile organic compounds (VOCs). Specifically, the concentrations of phenethyl alcohol, 3‐methyl‐1‐butanol, ethyl octanoate, and decanoic acid were notably elevated in comparison with other groups. CONCLUSION: This study illustrates that Metschnikowia species, particularly M. koreensis, show significant potential as starters for cider due to their various technological properties, including acidity modulation, aroma enhancement, and color improvement. The findings of this study provide a foundation for improving cider quality by co‐fermenting S. cerevisiae with innovative starter cultures. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

To examine the variances in volatile organic compounds (VOCs) and sensory attributes across various hop cultivars, an analytical approach was employed. Specifically, gas chromatography-ion mobility spectroscopy (GC-IMS), gas chromatography-mass spectrometry (GC-MS), and quantitative descriptive analysis (QDA) were employed to scrutinize the VOCs and sensory characteristics of four distinct hop varieties, namely Magnum, Palisade, Saaz, and Hersbrucker. The outcomes of QDA revealed a diverse array of sensory profiles in the hops, encompassing citrus and non-citrus fruit aromas, woody, floral, herbal, spicy, and green aromas, with noticeable distinctions in sensory attributes discernible among the various hop cultivars. The results showed that 79 VOCs were identified in the GC-IMS spectra of different varieties of hops, including terpenes, alcohols, esters, aldehydes, and ketones. 140 VOCs were identified in the GC-MS spectra of different varieties of hops, including terpenes, alcohols, ketones, esters, acids, and aldehydes, with terpenes and esters emerging as the prevailing constituents in hops. The principal component analysis (PCA) of different hop VOCs was performed to effectively identify the differences among hop varieties. This study can provide a valuable reference for the comprehensive analysis of VOCs and sensory attributes in hops. Furthermore, it contributes theoretical underpinnings to inform the precise application of hops in the context of beer brewing. [ABSTRACT FROM AUTHOR]

Strong-flavor Daqu, as a fermentation agent, plays a significant role in shaping the quality of strong-flavor baijius, and fungal species in Daqu are important factors affecting the quality of Daqu. Therefore, we selected strong-flavor Daqu from seven different origins to study the fungal composition and the effects of the fungal composition on the physicochemical properties and volatile organic compounds (VOCs). It was found that the fungal composition influences the physicochemical properties of Daqu. Specifically, there was a positive link between Rhizomucor, Rhizopus, Thermomyces, and liquefying activity and a positive correlation between Aspergillus and fermenting activity. Furthermore, the relationships between esterifying activity and Thermomyces, Rhizomucor, Aspergillus, Pichia, and Saccharomycopsis were found to be positive. The VOCs in Daqu were affected by Aspergillus, Issatchenkia, Pichia, and Thermoascus. Issatchenkia was significantly positively correlated with benzeneethanol as well as Aspergillus and pentadecanoic acid ethyl ester, ethyl myristate. Pichia and Thermoascus were significantly negatively correlated with benzaldehyde and 2-furaldehyde. This study deepens our understanding of the relationship between VOCs, the physicochemical properties with microbial communities, and reference significance for the production of better-quality strong-flavor Daqu. [ABSTRACT FROM AUTHOR]