| Summary: | 碩士 === 輔仁大學 === 食品科學系 === 101 === Pork is one of the most important farm products in Taiwan. Understanding the effects of pig breeds and parts on pork quality, and establishing an objective method for quality evaluation are necessary for the consideration of the improvement in pork quality and its economic value. Therefore, the objectives of this study were to investigate the quality of loin and of belly from different pig breeds, and to study the rheological properties and microstructure of raw and cooked pork from different pig breed and parts. This research was generally divided into two parts. The first part was focus on the quality characteristic, where the chemical composition, color, water-holding capacity, drip loss, marbling and the texture of pork loin and of belly from Berkshire, LeeSung-LuChuan and LYD three-breed cross pigs were analyzed. The marbling score was obtained by using the Pork Meat Rating System. The second part placed emphasis on the rheological property and the microstructure of raw and cooked pork from the loin and belly. The stress relaxation of pork was measured by using the texture analyzer. The composition distribution and microstructure of pork were observed by using the confocal-laser scanning microscope. The results showed that Berkshire pork had the lowest water-holding capacity and consequently the highest drip loss. Berkshire loin had the lowest moisture content but the highest in fat and in protein contents and also in marbling score. The belly of LeeSung-LuChuan had the highest moisture and protein content but the lowest in fat content, and the lightest in color. The pork color of LYD was dark and red. The hardness of LYD loin and LeeSung-LuChuan belly was the highest. In stress relaxation, the viscoelastic parameters of linear model showed that the elasticity (K2) of pork belly and loin increased after cooking. According to the result of microstructure and chemical composition of pork, the change in elastic parameters (E1 and E2) of two-element Maxwell model could be related to moisture. The shorter relaxation time (λ1) could relate to the connective tissue protein, collagen. The longer relaxation time (λ2) could relate to the muscle fiber protein. Thermal coagulation and shrinkage of muscle fibers in pork loin and belly during cooking were observed by confocal laser scanner microscope. These changes might lead to the change in relaxation times (λ1 and λ2). The methods developed in this study are able to observe the differences in meat quality of pork loin and belly from three pig breeds. The rheological property and microstructure of meat are able to explain the changes in meat quality during cooking.
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