Number of denatured rigor cross-bridges determines the intracellular volume shrinkage in porcine muscle fibre under PSE-inducing condition

Earlier onset of rigor mortis is a critical physiological progress occurring in the development of pale soft and exudative (PSE) meat. However, how rigor cross -bridges denature under different physiological conditions and their impacts on water -holding capacity remains unclear. To address this scientific question, we firstly established a method to quantify the extent of rigor cross -bridge denaturation using skinned fibres prepared from porcine longissimus thoracis et lumborum muscle. Effects of pH and temperature on the kinetics of rigor crossbridge denaturation, actomyosin denaturation and shrinkage of muscle fibre were studied. We then manipulated the number of rigor cross -bridges before the denaturation condition was initiated (pH 5.5, 38 degrees C). Results suggested that the loss of water -holding capacity in PSE meat is determined by the number of denatured rigor cross -bridges. Physiochemical analysis on myofibrils demonstrated that increase in protein oxidation, surface hydrophobicity and loss of electrostatic repulsive force between myofibrils may be involved in the mechanism.