Wet aging is generally defined as holding beef under vacuum and refrigerated temperatures for a period post-mortem. Wet aging has successfully been utilized to improve beef tenderness. It is well understood that, with time, proteolytic enzymes progressively reduce myofibrillar structures and allow for a more fragmented myofibril, which is easier to chew or shear. Previously, it has been demonstrated that tenderness is related with time up to a point. For most muscles ultimate tenderness is realized between 21 and 28 days (NCBA, 2006). However, extended aging, beyond 21 or 28 days, is a common practice employed to ensure tenderness, while also imparting alterations to beef flavor.
Beef flavor is derived, in part, from free-amino acids that participate in the initial stages of the Maillard reaction and the subsequent Strecker degradation. Checkoff funded work completed by our research team (FY2017), in agreement with prior works, strongly supports the accumulation of free-amino acids in beef during extended aging (Foraker, 2018). Likewise, our work has indicated that increases in free-amino acids contribute to beef flavor development. Recent work completed by our group further demonstrated the association of proteolytic activity and free-amino accumulation contributions to beef flavor (Vierck et al. 2019). Overall it may be concluded that both tenderness and flavor development are aided by proteolytic activity during wet aging. While tenderness may not significantly change with extended aging, flavor is altered with extended aging.
The objective of this work is to evaluate the influence of wet aging temperature, duration, and the interaction of these factors on consumer liking, objective measures of beef palatability, and indicators of proteolytic activity and spoilage organism growth.
Paired beef strip loins (IMPS 194) were collected from USDA Low Choice carcasses (n=60) free of quality defects. Each carcass was assigned to an aging temperature (-2, 0, 4℃). Loins from each carcass were cut in half and each loin portion was assigned to an aging duration (14, 28, 42, 56 d). At each aging interval loins were aseptically opened and swabbed for microbial analysis, fabricated in 2.54 cm steaks, and stored at -20℃ until subsequent analyses. Steaks were assigned to consumer sensory panel, descriptive sensory panel, shear force/volatile compound analysis, or raw analyses. Raw steaks (n=240) were homogenized into a fine powder. Raw samples were subjected to free amino acid analysis, desmin and troponin-t degradation, and targeted raw volatile compound analysis. Steaks for cooked analyses (n=240) were cooked in an electric combi-oven set at 204℃ and 0% humidity to reach an internal temperature of 71℃. Trained panelists evaluated steaks for 16 beef flavor and texture attributes. Consumer panelists evaluated steaks for flavor, tenderness, juiciness, and overall liking. All descriptive and consumer sensory attributes were evaluated using a 100 point scale where (0 = extremely tough/dry/not detectable ; 100 = extremely tender/juicy/intense). Following, slice shear force, the remaining cooked steak portion was homogenized for targeted cooked volatile analysis.
Aging at 4℃ for extended periods of time resulted in increased spoilage organism counts, protein degradation, free amino acid content, and off-flavor development. Contrastingly, aging at -2℃ inhibited spoilage organism growth and proteolytic activity, which resulted in impeded flavor and tenderness development. Aging duration should be considered when holding cooler temperatures at different levels.
Cold chain management in combination with postmortem aging may be utilized to promote desirable tenderness and flavor. Warmer temperatures may require shorter durations to achieve optimal tenderness. While colder temperatures may require longer durations to achieve optimal tenderness. Flavor may deteriorate more rapidly in warmer temperatures. However, regardless of temperature aging to approximately 42 days achieves similar sensory outcomes when initial microbial counts are reasonably low and vacuum packaging remains sound. There appears to be little advantage to aging strip loins beyond 42 days.