Department of Animal Science, Iowa State University, Ames, IA 50011, USA.
Meat Sci. 2010 Sep;86(1):184-95. doi: 10.1016/j.meatsci.2010.05.004. Epub 2010 May 20.
It is certain that meat tenderness is a highly valued consumer trait and thus definition of the multiple processes that influence meat tenderness will provide clues toward improving meat quality and value. The natural process by which meat becomes tender is complex. Tenderness development is dependent on the architecture and the integrity of the skeletal muscle cell and on events that modify those proteins and their interaction. Specifically protein degradation and protein oxidation have been identified as processes that modify proteins as well as the tenderness of meat. The intracellular environment is a major factor that controls these events. Ultimately, the interplay between these events determines the rate and extent of tenderization. Given the intricacy of the structure of the muscle cell, coupled with the complexity of the regulation of protein modification and the ever-changing intracellular environment it is not surprising that this area of research is a very dynamic field. Just as the overall integrity and function of muscle cells does not depend on a single protein, but rather on the coordinated interaction of several proteins, the structural weakening of muscle cells during postmortem aging also must not depend on the degradation of a single myofibrillar or other cytoskeletal protein. The proteins mentioned in this review are located in different regions of the muscle cell, and most have been implicated in some manner as being important in maintaining the structure and function of the muscle cell. Oxidation of myosin heavy chain, a predominant protein in the myofibril, is known to promote aggregation and toughening of meat. Degradation of proteins such as desmin, filamin, dystrophin, and talin (all located at the periphery of the Z-line) may disrupt the lateral register and integrity of the myofibril themselves as well as the attachments of the peripheral layer of myofibril to the sarcolemma. Degradation of the proteins within the myofibril that are associated with the thick and thin filaments may allow lateral movement or breaks to occur within the sarcomeres of postmortem aged samples. Titin, nebulin, and troponin-T, by their ability to directly interact with, or modulate the interaction between, major proteins of the thick and thin filaments and (or) the Z-line, play key roles in muscle cell integrity. Disruption of these proteins, especially titin and nebulin, could initiate further physicochemical and structural changes that result in myofibril fragmentation and loss of muscle cell integrity, and ultimately in tenderization of the muscle. In order to make real progress in this area, the scientific community must have a global appreciation of how both the structural proteins and the key proteases are influenced by the vast changes that occur during the conversion of muscle to meat.
可以肯定的是，肉质的嫩度是消费者非常重视的特性，因此，对影响肉质嫩度的多种过程进行定义将为改善肉质和价值提供线索。肉变得嫩的自然过程是复杂的。嫩度的发展取决于骨骼肌细胞的结构和完整性，以及改变这些蛋白质及其相互作用的事件。具体来说，蛋白质降解和蛋白质氧化已被确定为改变蛋白质和肉嫩度的过程。细胞内环境是控制这些事件的主要因素。最终，这些事件的相互作用决定了嫩化的速度和程度。鉴于肌肉细胞结构的复杂性，加上蛋白质修饰的调节的复杂性和不断变化的细胞内环境，这个研究领域是一个非常动态的领域也就不足为奇了。就像肌肉细胞的整体完整性和功能不依赖于单个蛋白质，而是依赖于几种蛋白质的协调相互作用一样，肌肉细胞在死后老化过程中的结构弱化也不依赖于单个肌原纤维或其他细胞骨架蛋白的降解。本文所述的蛋白质位于肌肉细胞的不同区域，大多数蛋白质都以某种方式被认为对维持肌肉细胞的结构和功能很重要。肌球蛋白重链的氧化是肌原纤维中的主要蛋白质，已知会促进肉的聚集和变坚韧。诸如结蛋白、细丝蛋白、营养不良蛋白和桩蛋白（都位于 Z 线的外围）等蛋白质的降解可能会破坏肌原纤维本身以及肌原纤维外围层与肌细胞膜的附着的横向注册和完整性。与粗丝和细丝相关的肌原纤维内的蛋白质的降解可能会导致死后老化样品的肌节内发生横向运动或断裂。肌联蛋白、nebulin 和肌钙蛋白-T 通过其直接相互作用或调节粗丝和细丝以及（或）Z 线的主要蛋白质之间相互作用的能力，在肌肉细胞完整性中发挥关键作用。这些蛋白质的破坏，特别是肌联蛋白和 nebulin 的破坏，可能会引发进一步的物理化学和结构变化，导致肌原纤维的碎片化和肌肉细胞完整性的丧失，并最终导致肌肉的嫩化。为了在这一领域取得真正的进展，科学界必须全面了解结构蛋白和关键蛋白酶是如何受到肌肉转化为肉的巨大变化的影响的。
