Isolation of psychrotolerant protease-producing yeast strains from dry-aged beef and evaluation of their beef protein degradation ability

In this study, microbial isolation techniques were applied to dry-aged Yanbian yellow cattle beef to obtain functional yeast strains. Based on assessments of protease activity, antibacterial capability, and growth performance, six low-temperature-tolerant protease-producing yeasts were successfully screened. A yeast strain capable of promoting sweet-tasting amino acids and increasing 2-ethylhexanol levels in beef was obtained through a beef protein–based simulated fermentation experiment. Molecular identification confirmed this strain, designated SN-20, as Millerozyma farinosa . SN-20 exhibits strong protease-producing ability and notable low-temperature tolerance. It increases TCA-soluble peptide content, promotes the formation of sweet-taste amino acids, and enhances the accumulation of volatile flavor compounds. Through the action of its secreted proteases, SN-20 accelerates muscle protein hydrolysis and facilitates the generation of flavor-active substances, thereby contributing to improved beef flavor quality. Overall, this work provides a basis for developing high-quality starter cultures and advancing fermentation-assisted dry-aging technologies. • Screen psychrotolerant protease-producing yeasts from dry-aged beef and identify Millerozyma farinosa SN-20 as a highly active strain with strong low-temperature adaptability. • Demonstrate the exceptional proteolytic capacity of SN-20, which significantly increases TCA-soluble peptides and accelerates myofibrillar protein hydrolysis at 4 °C. • Enhance the accumulation of sweet- and umami-related free amino acids, particularly Ser, Gly, Ala, Glu, and Asp, through SN-20-driven proteolysis. • Promotes the formation of key aroma-active volatiles, including 2-ethylhexanol, aldehydes, ketones, and esters, thereby enhancing flavor richness and diversity in meat products. • Provide a scientific basis for developing psychrotolerant starter cultures to improve flavor quality and processing efficiency in fermentation-assisted dry-aging systems.