抄録
Effects of drying temperature on dehydration progress and the quality of salted-dried meat were investigated. When drying at 20 ˚C, dehydration of salted fish meat proceeded more rapidly than unsalted fish meat. Although moisture in the inside of unsalted fish meat barely decreased during the dehydration process, a moisture decrease was observed in the inside as well as on the surface of salted fish meat, indicating that moisture migration from the inside to the surface of fish meat was promoted by salting. NaCl content on the surface of salted fish meat was much higher than that in the inside irrespective of drying duration, suggesting sluggish internal migration of NaCl during the dehydration process. A NaCl gradient formed in the inside of fish meat generated the difference in water holding capacity on the surface and the central part of fish meat. Consequently, internal moisture migration was promoted along with the NaCl gradient in salted fish meat. When drying at 40 ˚C, internal moisture migration was promoted due to lowering of the water holding capacity of unsalted fish meat. In addition, the NaCl gradient was not observed in the inside of salted fish meat by the promotion of NaCl migration. As a result, the promoting effect of salting on the progress of dehydration was no longer seen when drying at 40 ˚C.
Inactivation of Ca-ATPase and decrease in salt solubility of myofibrillar protein in salted-dried fish meat proceeded extensively when drying at 40 ˚C, demonstrating much more rapid progress of protein denaturation than at 20 ˚C. The changes in mobility of moisture and NaCl above mentioned were probably because denaturation of myofibrillar protein progressed at 40 ˚C. Extensive protein denaturation proceeded even in semi-dried product with more than 60% moisture, by the dehydration at 40 ˚C. The amounts of centrifugal and cooking drip of semi-dried product dried at 40 ˚C were larger than those at 20 ˚C, suggesting that water holding capacity of fish meat decreased due to protein denaturation.
These results suggested changes in the biochemical properties of myofibrillar protein in fish meat by salting and dehydration were closely related to the progress of dehydration as well as the quality of salted-dried fish meat.
