Abstract
The thermal behavior of actomyosin from the porcine skeletal muscle under various heating conditions including retort processing was examined. The physical properties (breaking energy, modulus of elasticity and water release rate) of the heat-induced gels of actomyosin decreased with increasing heating temperature or heating rate. The microstructure of the gel exhibiting lower physical property values had an aggregated-type structure, whereas the microstructure of the gel exhibiting higher physical property values had a strand-type structure as determined by scanning electron microscopic observation. It was considered that low physical property values of retorted gel of actomyosin were dependent on the network formation producing aggregated-type microstructure. This consideration was also strongly supported by the results of image analysis on microstructure of actomyosin gels under various heating conditions. The denaturation behavior of the actomyosin and components of the heat-induced gel of actomyosin were analyzed by differential scanning calorimetry, sodium sulfate-polyacrylamide gel electrophoresis, and western-blot analyses. The results suggested that the aggregated-type microstructure induced by retorting was caused by a shift in the denaturation transition temperatures of myosin to higher temperatures, an increase of the denaturation energy of myosin, and in gel formation of a large protein complex composed of myosin and actin.
