Impacts of Stepwise Aging/Freezing Process and Repeated Freezing on Meat Quality, Physicochemical and Biochemical Properties, and Sensory Attributes of Beef Loins

The study aimed to investigate the impact of aging durations prior to and after repeated freezing/thawing cycles on the quality attributes of beef loins. At 2 d postmortem, paired beef loins from 30 carcasses were divided into aging groups (0, 2, 3, and 4 weeks at 2°C) named A0, A2, A3, and A4, respectively. Sections from each group were taken as never-frozen samples (F0T). The 4-week aged subsections were stored for an extra week as long-term aged-only controls (A5). The remaining portions were frozen for 1 to 5 weeks, creating a total aging/freezing cycle of 5 weeks. After the initial freezing periods, samples were thawed and collected as aged/frozen samples (F5T, F3T, F2T, F1T). The remaining portions were frozen again for 5 weeks and thawed as repeated frozen/thawed samples (F5T × 2, F3T × 2, F2T × 2, F1T × 2). Aging significantly reduced freeze/thaw losses, with the least losses observed in 4-week-aged, one-time frozen samples (A4F1T; P < 0.05). Repeatedly frozen samples exhibited lower losses compared to one-time frozen samples. Cooking loss was not different between never-frozen and aged/frozen samples (P > 0.05). In non-aged samples, instrumental tenderness significantly decreased with repeated freezing (A0F5T × 2), comparable to 5-week aged-only (never-frozen) samples (A5F0T; P > 0.05). The myofibrillar fragmentation index increased with aging coupled with freezing (P < 0.05). Lipid oxidation was increased in 4-week-aged, repeatedly frozen samples (A4F1T × 2, P < 0.05). Carbonyl content increased with aging and freezing processes (P < 0.05). Repeated freezing adversely affected display color stability compared to never-frozen samples. The consumer panel (n = 90) found no differences in eating quality attributes (P > 0.05), regarding liking of tenderness, flavor, juiciness, and overall liking between the aging/freezing samples. The results of the study suggest that stepwise aging/freezing can provide protective effects against moisture loss during freezing and repeatedly frozen/ thawed processes, likely due to increases in muscle fragmentation. Stepwise aging/freezing can be a viable approach for the meat industry for the consistent supply of frozen beef with quality equivalent to fresh meat.