Huff-Lonergan E, Parrish F C, Robson R M
Department of Animal Science, Iowa State University, Ames 50011, USA.
J Anim Sci. 1995 Apr;73(4):1064-73. doi: 10.2527/1995.7341064x.
This study was conducted to determine degradation of the giant myofibrillar proteins titin and nebulin in postmortem aged beef, with known tenderness values, from animals differing in sex (steers vs bulls) and age (cows vs steers and bulls). Ten bulls and 10 steers (both groups were approximately 14 mo old) and 10 cows (44 to 108 mo old) were slaughtered. Longissimus muscle samples were removed for determination of Warner-Bratzler shear force, sensory panel tenderness evaluation, and SDS-PAGE analysis at 3, 7, 14, and 28 d postmortem. The SDS-PAGE analysis of titin and nebulin revealed that titin often migrated as three closely-spaced bands (T1, T1-2, T2, in increasing order of migration) in 3-d postmortem samples. With increasing time post-mortem, intact titin (T1) decreased and degraded titin (T2) increased in all samples. Within a class (i.e., steers, bulls, or cows) the rate of conversion of T1 to T2 was slower in the less-tender samples. The T1 to T2 conversion postmortem was slower in the intact males (bulls) than in the castrated males (steers). The T1 to T2 conversion postmortem also was slower in the older animals (cows) in comparison to the younger steers, but not in comparison to the younger bulls. Nebulin was degraded by 3 d postmortem in tender samples from steers, but some nebulin remained in the less-tender 3-d samples from steers and in all of the 3-d samples from bulls and older animals (cows). Intact nebulin was absent in all 7-d samples, regardless of the class of animal. Our results suggest that titin and nebulin are degraded at faster rates in more tender beef samples within each of the three classes of animals examined. The rate of degradation seems to differ when sex and age classifications are compared.
本研究旨在确定已知嫩度值的宰后陈化牛肉中，肌联蛋白和伴肌动蛋白这两种巨大的肌原纤维蛋白的降解情况，这些牛肉来自性别（阉牛与公牛）和年龄（母牛与阉牛和公牛）不同的动物。屠宰了10头公牛和10头阉牛（两组年龄均约为14月龄）以及10头母牛（44至108月龄）。取出背最长肌样本，用于测定宰后3、7、14和28天的沃纳-布拉茨勒剪切力、感官评定小组的嫩度评估以及SDS-PAGE分析。对肌联蛋白和伴肌动蛋白的SDS-PAGE分析显示，在宰后3天的样本中，肌联蛋白通常以三条紧密相邻的条带形式迁移（按迁移顺序依次为T1、T1-2、T2）。随着宰后时间的增加，所有样本中完整的肌联蛋白（T1）减少，降解的肌联蛋白（T2）增加。在同一类别（即阉牛、公牛或母牛）中，嫩度较低的样本中T1向T2的转化速率较慢。宰后T1向T2的转化在完整雄性（公牛）中比去势雄性（阉牛）中慢。与年轻阉牛相比，老年动物（母牛）宰后T1向T2的转化也较慢，但与年轻公牛相比则不然。伴肌动蛋白在阉牛嫩度较高的3天样本中在宰后3天就被降解，但在阉牛嫩度较低的3天样本以及公牛和老年动物（母牛）的所有3天样本中仍有一些伴肌动蛋白残留。所有7天样本中均不存在完整的伴肌动蛋白，无论动物类别如何。我们的结果表明在所检测的三类动物中，更嫩的牛肉样本中肌联蛋白和伴肌动蛋白的降解速率更快。当比较性别和年龄分类时，降解速率似乎有所不同。
