Traditionally, beef is aged and then frozen to extend shelf life, but recent studies suggest that freezing before aging may further enhance tenderness. While freezing has been associated with quality loss and negative consumer perception, these concerns have been challenged by newer research, which found improved tenderness and shear force scores in frozen meat regardless of aging duration. The hypothesis that freezing inactivates calpastatin and hereby enhancing proteolytic activity, is supported by studies showing calpastatin decline during frozen storage, especially at -80ºC. Additionally, muscle-specific improvements in tenderness and desmin degradation were observed in frozen-then-aged treatments. However, variability due to breed and other factors means the mechanism remains unclear. There have been few studies to evaluate the palatability impact of freezing and then aging beef steaks and none that have evaluated the impact on the consumer’s eating experience. Therefore, the objective of this study is to understand the eating quality impact of frozen and then aged beef steaks of different muscles and different aging periods. Thus, the objective of this study was to determine if different aging and freezing combinations impact the consumer’s overall eating experience, objective tenderness, cook loss, and cooked internal color.
Twelve USDA Low Choice, A-maturity beef carcasses were selected. Strip loins (IMPS #180) and goosenecks (IMPS #170) were collected to isolate the Longissimus lumborum (LL), Biceps femoris (BF), and Semitendinosus (ST) muscles. These muscles were chosen for their known variability in tenderness and responsiveness to postmortem interventions. Each muscle was portioned into four sections and randomly assigned to one of four treatments: aging for 21 or 28 days then freezing (21AF, 28AF), or freezing immediately and aging for 21 or 28 days (21FA, 28FA). Steaks were sliced at 2.54 cm and then were assigned to consumer panels, shear force, or lab assays. The AF samples were frozen at -20°C for 30–37 days and thawed before testing. The FA samples followed the same freezing parameters in reverse order.
There were minimal statistical differences found within consumer ratings. A significant interaction for juiciness (P < 0.05) revealed the Longissimus lumborum (LL) was rated the juiciest, and the Biceps femoris (BF) was rated the least juicy, regardless of treatment. Interestingly, the Semitendinosus (ST) showed higher juiciness in the 21-day frozen-then-aged (FA) treatment compared to the aged-then-frozen (AF) counterpart, but this effect disappeared at 28 days, suggesting aging time may influence freezing order effects on juiciness.
For tenderness and overall liking, no significant interactions on freezing or aging treatment effects were detected (P > 0.05); only muscle type affected these traits. The LL scored the highest (P < 0.05) ratings for tenderness, while the BF scored the lowest tenderness ratings indicating it was perceived to be the toughest. The overall liking followed the same pattern, with the LL receiving the highest overall liking scores and the BF receiving the lowest. The consumer acceptability data followed the same pattern in which the highest (P < 0.05) percentage of consumers rated the LL as acceptable for all palatability traits. While it was surprising to find the freezing treatment did not impact any palatability trait besides juiciness, it is well documented that the BF and ST have a significant decrease in palatability in comparison to the LL.
Similar to the consumer panel results, there were no interactions for Warner-Bratzler shear force (WBSF), purge loss, or cook loss. Consistent with sensory data, the BF had significantly higher WBSF values compared to the LL (P < 0.05), while aging period and freezing treatment had no effect (P > 0.05). The FA samples had higher purge loss (P < 0.05) but lower cook loss (P < 0.05) compared to the AF counterparts. This phenomenon is consistent with the water-loss tradeoff previously observed. However, this increase in purge loss remains a concern for industry adoption.
The hypothesis of this project was that reversing the freezing and aging order would improve tenderness through heightened proteolytic activity, however these results do not support that hypothesis. The results indicate reversing the typical age and freezing order does not improve tenderness, but does increase purge loss, and therefore is not a valid way to improve palatability of historically tough muscles.
ARMS#010226-09