新疆褐牛不同部位肉宰后成熟过程中蛋白降解变化研究

为研究肌纤维类型对新疆褐牛肉宰后成熟过程中蛋白质降解变化的影响,选取背最长肌、腰大肌和股二头肌3个不同肌纤维类型组成的部位肉,分别在宰后4℃成熟1 h、6 h、12 h、1 d、3 d、7 d、14 d研究其蛋白质溶解度、肌原纤维小片化指数、肌纤维超微结构变化及进行十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)分析。结果表明:不同肌纤维类型的新疆褐牛肉蛋白质降解模式差异较大,Ⅰ型肌纤维含量高的腰大肌比Ⅱ型肌纤维含量高的背最长肌和股二头肌具有更高的初始肌原纤维小片化指数(MFI),但肌原纤维降解的速度比背最长肌和股二头肌要慢。ⅡA型肌纤维含量与初始蛋白质溶解度呈显著正相关,与蛋白质溶解度的变化率显著负相关。不同肌纤维类型组成的新疆褐牛肉在宰后成熟过程中蛋白质降解变化存在差异,研究结果可为宰后成熟过程合理控制、新疆褐牛肉产品开发提供理论依据。     

Myofibrillar proteins in white muscle of the developing African catfish Heterobranchus longifilis (Siluriforms, Clariidae)

Developmental changes in myofibrillar protein composition were investigated in the myotomal muscle of the African catfish, Heterobranchus longifilis (Clariidae), by several electrophoretic techniques. The main muscle fibres of larvae and the fast-white muscle fibres of juvenile and adult fish were found to express distinct myosin heavy chain and myosin light chain 2 (LC2) isoforms. Three myosin LC2 chains were successively detected, differing by their isoelectric points. In contrast, the alkali light chains remained qualitatively and quantitatively unchanged during fish growth. Actin, -tropomyosin, and troponin-C (TN-C) were also similar in larval, juvenile, and adult white muscle, but an additional larval tropomyosin isoform was found in the first developmental stages. Two isoforms of troponin-T (TN-T) and troponin-I (TN-I) were synthesised in the course of fish growth. Transition from the larval to the adult isoform was much faster for TN-T than for TN-I. Slow-red muscle myofibrils from adult H. longifilis showed no common component (except actin) with larval, juvenile, or adult fast-white muscle myofibrils. Red myofibrils displayed a single TN-T and a single TN-I isoform, but two isoforms of TN-C. The myofibrillar protein isoforms synthesised at any given developmental stage almost certainly reflect changes in the functional requirements of swimming muscles in the course of fish development.     

电刺激对宰后牦牛肉ATP、calpain活力和细胞骨架蛋白降解的影响

为了研究低压电刺对牦牛肉ATP、Calpain活力和细胞骨架蛋白降解的影响及其嫩化机理,将24头甘南牦牛随机分为2组,每组12头,屠宰,按试验设计对宰后牦牛胴体进行电刺激(ES)(输出电压21V、功率50W、时间90s)和常规冷却排酸NES(0~4℃、风速0.5m/s)处理,并于0、24、72h测定牦牛背最长肌的ATP、calpain活力、糖原、剪切力值和细胞骨架蛋白降解情况.结果表明:宰后72hATP下降了14.97%,较NES组下降幅度达6.59%,ES显著提高了ATP的下降速率;宰后0h,ES组糖原较NES组低12.46%,加快了糖酵解速率;ES组在宰后0hm-calpain和μ-calpain较NES组活力分别提高了0.318U/mL和0.31U/mL,同时提高了m-calpain和μ-calpain活力,过早激活了μ-calpain;ATP与m-calpain有极显著的负相关性(P<0.01),而μ-calpain与糖原含量、剪切力三者相互之间有极显著的正相关性(P<0.01);低压电刺激极显著提高牦牛肉最终嫩度(P<0.01);电刺激在速度和数量上显著加速了Desmin和Troponin-T的降解,加快了牦牛肉成熟,缩短了成熟时间.