The objective of this study was to determine effects of extended aging and intramuscular location on Warner-Bratzler shear force (WBSF), muscle fiber cross-sectional area (CSA), and protein degradation of semitendinosus (ST) and longissimus lumborum (LL) steaks. Left ST and LL were removed from 40 carcasses at 6 d postmortem. The ST was fabricated into five locations (LOC), with LOC 1 being most proximal and LOC 5 being most distal. The posterior LL was fabricated into 3 LOC, with LOC 1 being most anterior. Vacuum sealed ST steaks were aged 7, 14, 28, 56, or 112 d postmortem, while LL steaks were aged 7, 28, or 112 d postmortem at 2 ± 1 °C. A steak from each LOC was assigned to WBSF or laboratory analyses. There were no Day of Aging (DOA) × LOC interactions for all dependent variables (P > 0.06). There were DOA effects for ST and LL WBSF values and degraded 38-kDa desmin (DES; P < 0.01). Day-7 ST-steak WBSF value was greater than all other days (P < 0.01) and day-14 steaks had greater WBSF value than remaining days (P < 0.05). Day-28 ST-steak WBSF values were greater than day 56 and 112 (P < 0.01), which did not differ (P = 0.53). In the LL, day-7 steaks had greater WBSF values than the other two timepoints (P < 0.01) and day-28 steaks had greater (P < 0.01) WBSF values than day-112 steaks. Degraded ST 38-kDa DES content was less on day 7 and 14 compared to all other days (P < 0.03), but did not differ (P = 0.79) from each other. Days 28 and 56 38-kDa DES content was less than day 112 (P < 0.01), but did not differ (P = 0.34) from each other. Degraded LL 38-kDa DES content was less on day 7 than day 28 and 112 (P < 0.02), which did not differ (P = 0.67). There were LOC effects for only ST WBSF and muscle fiber CSA (P < 0.05). Semitendinosus steak LOC 1 and 2 had greater WBSF values than all other locations (P < 0.01), but did not differ (P = 0.32) from each other. Semitendinosus steak LOC 3 and 5 had greater WBSF values than LOC 4 (P < 0.01), but did not differ (P = 0.85) from each other. The CSA of all ST fiber types were largest in LOC 1 compared to all other fiber types (P < 0.01). The CSA of all LOC 2 and 3 fiber types was greater than LOC 4 and 5 (P < 0.01), but were not different from each other (P > 0.81), and LOC 4 had greater CSA than LOC 5 (P < 0.01). Steak aging WBSF value improvements seemed proteolysis catalyzed, while the ST intramuscular tenderness gradient was more likely due to muscle fiber CSA.

中文翻译：

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延长死后老化和肌肉定位对腰最长肌和半腱肌牛排蛋白质降解、肌纤维形态和嫩度的影响

本研究的目的是确定延长老化和肌肉内定位对 Warner-Bratzler 剪切力 (WBSF)、肌纤维横截面积 (CSA) 以及半腱肌 (ST) 和腰最长肌 (LL) 牛排的蛋白质降解的影响. 死后 6 天从 40 具尸体中取出左侧 ST 和 LL。ST 被制造成五个位置 (LOC)，其中 LOC 1 位于最近端，LOC 5 位于最远端。后部 LL 被制作成 3 个 LOC，其中 LOC 1 是最前面的。真空密封的 ST 牛排在 7、14、28、56 或 112 天死后陈化，而 LL 牛排在 2 ± 1 °C 下陈化 7、28 或 112 天。来自每个 LOC 的牛排被分配到 WBSF 或实验室分析。所有因变量没有老化日 (DOA) × LOC 交互作用 (P > 0.06)。ST 和 LL WBSF 值有 DOA 影响，38 kDa 结蛋白降低（DES；P < 0.01）。第 7 天 ST 牛排 WBSF 值高于所有其他天（P < 0.01），第 14 天牛排的 WBSF 值高于其余天（P < 0.05）。第 28 天 ST 牛排 WBSF 值大于第 56 天和第 112 天（P < 0.01），两者没有差异（P = 0.53）。在 LL 中，第 7 天牛排的 WBSF 值高于其他两个时间点（P < 0.01），第 28 天牛排的 WBSF 值高于（P < 0.01）第 112 天的牛排。与所有其他天相比，第 7 天和第 14 天降解的 ST 38-kDa DES 含量较少（P < 0.03），但彼此之间没有差异（P = 0.79）。第 28 天和第 56 天 38-kDa DES 含量低于第 112 天 (P < 0.01)，但彼此没有差异 (P = 0.34)。第 7 天降解的 LL 38-kDa DES 含量低于第 28 天和第 112 天 (P < 0.02)，两者没有差异 (P = 0.67)。仅 ST WBSF 和肌纤维 CSA 存在 LOC 效应（P < 0.05）。半腱肌牛排 LOC 1 和 2 的 WBSF 值高于所有其他位置 (P < 0.01)，但彼此没有差异 (P = 0.32)。半腱肌牛排 LOC 3 和 5 的 WBSF 值高于 LOC 4 (P < 0.01)，但彼此没有差异 (P = 0.85)。与所有其他纤维类型相比，所有 ST 纤维类型的 CSA 在 LOC 1 中最大（P < 0.01）。所有 LOC 2 和 3 纤维类型的 CSA 均大于 LOC 4 和 5 (P < 0.01)，但彼此没有差异 (P > 0.81)，并且 LOC 4 的 CSA 大于 LOC 5 (P < 0.81) ; 0.01)。牛排老化 WBSF 值的改善似乎是由蛋白水解催化的，