Abstract
This study was performed to clarify structural changes in collagen, changes in ASC, PSC and ISC contents, caused by moist heating for a prolonged period, and accompanying changes in lipid content, using kakuni pork as a sample. In addition, the influence of plant protease on these contents was also examined.
Regarding collagen content, no ISC was present, ASC content was significantly increased, and PSC content was significantly decreased after steaming. In the subsequent simmering process, the decrease in PSC content was not significant. When ginger juice or kiwifruit juice was added, no difference was noted in collagen content after steaming compared to that of the control. In the subsequent simmering process, PSC content decreased; a significant reduction was observed compared to the control when kiwifruit juice was added. This PSC content reduction in the simmering process may have resulted from protease action on the resultant collagen without globular domains during pre-treatment and heat-denatured regions of collagen in the early steaming phase. Fat and cholesterol decreased after cooking in all conditions. The contents were significantly reduced when kiwifruit juice was added compared to those of the control. These findings suggest that although heating weakens collagen fibers in pork chunks during cooking, a large amount of lipid is retained. The addition of kiwifruit juice further weakens the collagen fibers, increasing the dissolution of fat and cholesterol.
