魚肉の調理加工におけるタンパク質の変化 ＩＩ しめさば処理における魚肉の物性とタンパク質の変化

Abstract

Shimesaba (acid-salt curing) is a traditional Japanese fish processing where mackerel fillets are cured in vinegar after salting. In shimesaba, acid-salt cured muscle acquires a peculiar palatable texture. Experiments were carried out to clarify the nature of the changes in texture. Changes in muscle proteins were examined for the possible major factor of the texture changes. Five hours after adding 10% NaCl, mackerel muscle were soaked in rice vinegar at 4°C for 15h and 50h and were submitted to sensory tests. Muscle cured in vinegar for 50h were harder and more fragile than those stored for 15h. As a model of shimesaba, the mackerel fillets (1.5cm thick) were stored in 4% acetic acid-2% NaCl solution at 4°C for 7 days, and were submitted to the tests for firmness, fracturability and fragility, and the analysis of the proteins by SDS-PAGE at various storage periods. For control, fillets were stored by adding 2% NaCl or without any treatment. Firmness by texturometer test and fragility by author's disintegration method increased by acid-salt curing. SDS-PAGE patterns showed that proteins of acid-salt cured muscle were decomposed into fragments with smaller molecular weights during storage. Actomyosin and water soluble proteins extracted from the muscle underwent similar decomposition after acid storage. Decompositions of the proteins were proved as attributable to the acid proteinases in muscle which had been activated at the acidic pH's. The texture changes of the acid-salt cured mackerel muscle were attributed to the decomposition of the proteins due to the function of the proteinases activated at the acidic pH of the curing.