Combined Tumbling and Postmortem Aging to Improve Fresh Beef Quality, Palatability, and Proteolysis
Tenderness is a key sensory trait influencing beef palatability. Tumbling is a value-adding process that has been extensively applied and studied within the realm of processed meats. Various post-harvest strategies to ensure fresh beef reaches acceptable levels of tenderness have been employed, often with the aim of physically disrupting myofibrillar structure or enhancing the rate and extent of postmortem proteolysis. One such method would be the application of postmortem aging; however, the effectiveness of aging on tenderization is well-known to differ throughout individual muscles of the beef carcass. For inherently tough cuts, physical interventions such as mechanical tenderization are often used, although several detriments to quality attributes may be induced. Further, some modern consumers prefer meat products with no added non-meat ingredients. An alternative method of applying tumbling in the absence of a brine solution followed by additional postmortem aging could be a practical means to facilitate tenderization while potentially minimizing detriments to other eating quality attributes.
To evaluate the efficacy of tumbling without brine a method of beef tenderization, the process was first assessed in the longissimus lumborum muscle (n=9). In this study, muscles were allocated among 0, 60, and 90 minutes of tumbling, after which aging for 0, 7, and 14 days was conducted. Immediately after the application of the tumbling process, steaks from muscles that had been tumbled were considerably more tender (24.7 N and 21.6 N for 60 and 90 minutes, respectively) than non-tumbled controls (34.8 N). Steaks from the tumbled groups maintained greater instrumental tenderness throughout the course of the aging period. These results were supported by increases in myofibril fragmentation index, as well as increased troponin-T degradation during aging. However, cooking loss was increased in tumbled steaks, which could have implications for sensory juiciness. Considering this study demonstrated that tumbling without brine inclusion followed by postmortem aging resulted in profound changes to sensory traits, further study regarding its impacts on sensory attributes and proteolysis among different beef muscles was warranted.
The following study evaluated the combined tumbling and aging process on the quality, palatability, and proteolytic attributes of beef longissimus lumborum and semitendinosus muscles (n=16). Muscle sections were allocated among 0, 40, 80, and 120 minutes of tumbling, as well as 0 or 10 days of subsequent aging. Regardless of aging duration, tumbling for any duration increased instrumental tenderness of the longissimus lumborum but not semitendinosus muscle. Similar to the previous study, increased cooking loss was induced through tumbling. In both muscles, obvious fragmentation of the myofibrillar structure with tumbling was observed through increases in myofibril fragmentation index and transmission electron microscopy. Tumbling with aging favored the degradation of myofibrillar proteins including troponin-T and desmin; however, calpain-1 autolysis appeared mostly unchanged. Neither tumbling nor aging influenced the amount and properties of collagen, which may indicate why the process did not influence instrumental tenderness of the semitendinosus despite myofibrillar fragmentation and degradation. Longissimus lumborum muscles tumbled for any durations were rated by consumers (n=120) to be more tender with greater overall liking than control steaks. Semitendinosus steaks that were tumbled for 120 minutes and further aged had improved liking of tenderness with similar juiciness and flavor to control steaks at the same postmortem timepoint. These results indicated that tumbling without brine would result in myofibrillar fragmentation and favor the degradation of myofibrillar proteins during aging, while impacts on connective tissues would be minimal. Consequently, muscles without a high extent of background toughness would be effectively tenderized through tumbling, while the results would be more limited in inherently tough cuts.
Considering these results, the process was then applied to muscles of intermediate tenderness from the sirloin, specifically the gluteus medius, biceps femoris, and tensor fasciae latae muscles (n=16). Muscles were tumbled for 0 or 120 minutes, then aged for 0 or 10 additional days. Tumbling increased the instrumental tenderness of the gluteus medius and tensor fasciae latae but not the biceps femoris, regardless of aging time. Cooking loss was increased with tumbling in all muscles. Similarly, myofibrillar fragmentation was also increased in all muscles, and there was some evidence to suggest that tumbling with subsequent aging would aid in the degradation of troponin-T in the biceps femoris. To further understand how tumbling might affect specific descriptive sensory attributes, a trained panel (n=8) was conducted on aged samples. Tumbled gluteus medius steaks had greater myofibrillar tenderness than non-tumbled controls; however, tenderness scores of other muscles were not affected. There was some evidence that tumbling with aging could induce the generation of off-flavors in the gluteus medius and tensor fasciae latae, as well as decrease juiciness of the biceps femoris.
Taken together, these results support that tumbling without brine inclusion would be an effective strategy to improve beef tenderness and palatability, dependent on the traits of the individual cut. Improved tenderness would be primarily attributed to the fragmentation and degradation of myofibrillar structure. However, the results indicate that tenderization would be limited in cuts with a high extent of background toughness, which tumbling alone would be largely unable to disrupt. Future studies should focus on the effects of tumbling without brine inclusion with aging on oxidative stability and the potential introduction of hazards prior to industry application. Further elucidation of how the process could be optimized to maximize tenderization while minimizing potential negative impacts to flavor and juiciness would be beneficial to improving overall palatability.