Changes in free amino acid content and hardness of beef while dry-aging with Mucor flavus: Changes in the quality of beef while dry-aging with Mucor flavus

BACKGROUND: A mold strain thought to be suitable for dry-aging process was isolated. The information about the scientific aspects of molds related to dry-aging beef is scarce. We, therefore, conducted aging trials to determine the characteristics of the isolated mold strain associated with dry-aging process. Specifically, during the dry-aging of beef with the mold strain, the changes in the free amino acid content, hardness, productive loss, drip and cooking loss were analyzed. These characteristics were compared with those obtained while dry-aging in the absence of a mold. RESULTS: The isolated mold strain was identified as Mucor flavus. The free amino acid content in the mold-aging beef decreased or remained constant during the aging process. However, that in the trimming sections of the beef dramatically increased in the presence of mold. In addition, hardness of mold-aging beef gradually decreased during the aging process and finally decreased significantly. CONCLUSION: Amino acids such as GABA (gamma-aminobutyric acid), proline, and aspartic acid were produced by our mold strain, M. flavus during its growth on beef meat, and the mold conferred savory odors to the dry-aged beef.