宰后猪肌肉中空隙形成原因及其位置与汁液流失的关系

Drip loss is one of the important qualities of chilled meat; it has a major influence on sensory quality, the economic value and nutritional value of meat and meat products. Formation of drip loss is closely related to position and size of spaces caused by cytoskeleton degradation in the muscle post mortem. The qualitative and quantitative research on position and size of spaces in the muscle post mortem, comparative research on the relationship between the position and size of the spaces and drip loss of pork have not been reported, so understanding this relationship is not uniform. The aim of this project was to determine the desmin, integrin,vinculn, talin degradation, which is related to the formation of the spaces, changes of muscle microstructure of muscle post mortem with different drip loss and PSE meat by electron microscopy and tissue microscopic measurement techniques, while moisture status and distribution in meat were measured by low-field NMR techniques, then to analyze dose-effect relationship between size and position of the spaces, the target protein degradation, water status and distribution in muscle, drip loss, and to explore molecular mechanisms of formation of gaps inside and outside muscle cells and drip loss. This studies has important scientific significance for elucidating the mechanism of drip loss at the molecular level and microstructure level, and has an important value for guiding chilled meat production.

汁液流失是冷却肉的重要品质之一，对肉及肉制品的感官质量、经济价值、营养价值有重要影响。汁液流失的形成与宰后肌肉骨架蛋白降解导致的肌肉内空隙有密切关系，目前没有同时系统地对宰后肌肉内空隙进行定性(细胞内还是外)、定量（大小），空隙位置和大小与汁液流失率的关系进行比较研究，所以，对这种关系的认识并不统一。本项目用western bolt，电镜技术和组织微观测量技术对宰后不同汁液流失率肉样和PSE肉样中对空隙形成有关的desmin，integrin，vinculn，talin蛋白降解情况，肌细胞内外空隙变化情况进行测定，同时利用低场核磁共振技术对样中的水分状态情况进行测定，分析肌肉中空隙位置和大小与目标蛋白变化，水分状态和分布，汁液流失率的量效关系，探究肌细胞内外空隙形成和汁液流失形成的分子机理，该研究对从分子水平和组织微观结构层面阐明肌肉汁液流失机理有重要科学意义，对指导冷却肉生产有重要价值。

宰后45 min取40头猪的背最长肌样品，测定宰后45min和24 h肌肉色泽，用低场核磁共振(LF-NMR)测定宰后12 h和24 h肌肉T2弛豫时间，推算不易流动水（P21）和自由水（P22）的相对含量。测定宰后45min、3 h、9 h、12 h和24 h 骨架蛋白质变化、μ-calpain亚基，肌细胞内外空隙变化；采用聚类分析方法将样品分为高汁液流失组（H组）和低汁液流失组（L组），对测定指标进行组间比较，用偏最小二乘回归分析方法分析骨架蛋白质降解、肌细胞内外空隙和汁液流失之间的关系。结果显示：在宰后24 h，高汁液流失率组的P21显著低于液流失率组，而P22显著高于低汁液流失率组（P ＜ 0.01），P22与汁液流失率显著正相关（P ＜ 0.01）；宰后45 min 至12 h，H组的肌细胞外间隙高于L组（P ＜0.01）；宰后12h和24h时H组的μ-calpain 76kDa完整强度极显著低于L组（P＜0.01），宰后45min~24h，H组integrin完整强度在显著低于L组（P＜0.05），而talin的完整强度显著高于L组（P＜0.05），宰后3h~24h，H组的desmin完整强度显著高于L组（P＜0.05），而vinculin完整强度显著低于L组（P＜0.05）。细胞内间隙和细胞外间隙分别解释了汁液流失变化的16.5%和61.5%，而desmin、integrin和vinculin的完整强度分别解释了汁液流失变化的46.8%、33.7%和46.6%。宰后细胞内间隙的形成主要受integrin和vinculin的变化影响，而细胞外间隙的形成主要受desmin的变化控制。可见，宰后肌肉细胞内外间隙形成早，间隙大，会导致高汁液流失。细胞外间隙对汁液流失的影响大于细胞内空隙。该研究结果有助于在分子水平和组织微观结构层面解释肌肉汁液流失的机理。