Identification of Microorganisms Associated with the Quality Improvement of Dry-Aged Beef Through Microbiome Analysis and DNA Sequencing, and Evaluation of Their Effects on Beef Quality.

The objective of this study was to isolate and identify the microorganisms, especially yeasts and molds, related to the improvement of beef quality during dry-aging of beef through microbiome analysis, and to examine the possibility of using them as starter culture strains to improve the efficiency of dry-aging beef production. Beef sirloins were dry-aged for 28 days using different wind speeds (0, 2.5, and 5 m/s) at 1 to 3 °C and 75% relative humidity, and microbial compositions were confirmed by microbiome analysis. Mold and yeast samples were plated on potato dextrose agar supplemented with 10% tartaric acid, and the isolated colonies were identified by DNA sequencing. The isolates were subjected to microbial characterization (morphological characterization, growth condition, and enzyme activity). Microbiome analysis showed that the dominant microorganisms were molds and yeasts identified as Pilaira anomala SMFM201611 and Debaryomyces hansenii SMFM201707. Pilaira anomala SMFM201611 and D. hansenii SMFM201707 were inoculated into 24 sirloins of the lowest grade. All samples were dry-aged for 0, 14, 21, and 28 days and analyzed for microbial growth, pH, shear force, ultrastructure, and flavor compounds (free amino acids and free fatty acids). Inoculation with P. anomala SMFM201611 and D. hansenii SMFM201707 improved tenderness and cause the breakdown of myofibrils by proteolysis. Both microorganisms also produced free amino acids and fatty acids through proteolytic and lipolytic activities. These results indicate that P. anomala SMFM201611 and D. hansenii SMFM201707 isolated and identified from dry-aged beef can improve the quality of low-grade beef during dry-aging. PRACTICAL APPLICATION: During dry-aging, mold and yeast improve the quality of dry-aged beef. Pilaira anomala SMFM201611 and Debaryomyces hansenii SMFM201707 isolated from dry-aged beef can improve tenderness by breaking down myofibrils. Both microorganisms improve flavor by producing free fatty acids and amino acids, and the taste and aroma characteristics of low-grade beef may be improved during the dry-aging process.

Changes in microbial composition on the crust by different air flow velocities and their effect on sensory properties of dry-aged beef.

Beef rumps (middle gluteal) were dry aged for 28 days using different air flow velocities of 0, 2.5, and 5 m/s (DA0, DA2.5, and DA5, respectively). The microbial composition, physicochemical traits (moisture, pH, and shear force), flavor compounds (inosine 5'-monophosphate, reducing sugar, free amino acid, and free fatty acid), and electronic tongue profile were analyzed at day 0, 14, and 28. No molds or yeasts were detected until day 14. On day 28, Pilaira anomala was found to be the most abundant in DA0, whereas DA2.5 and DA5 showed increased composition of Debaryomyces hansenii. With that, the significant changes in physicochemical traits and flavor compounds occurred. In addition, the pattern of flavor compounds and taste attributes from DA0, which had different mold and yeast compositions, were discriminable from DA2.5 and DA5. Therefore, our results suggest that air flow can affect microbial composition on the crust, possibly resulting in different sensory properties of dry-aged beef.