Effect of high hydrostatic pressure (HHP) on myofibril-bound serine proteinases and myofibrillar protein in silver carp (Hypophthalmichthys molitrix)

Abstract

Silver carp (Hypophthalmichthys molitrix) is a popular cultured freshwater fish in China, and becomes a potential raw material for surimi product. However, silver carp surimi exhibits considerable gel softening (modori) and myofibril-bound serine proteinases (MBSP) involved in the degradation of myofibrillar proteins have been assumed to be crucial to the modori phenomenon. High-pressure technology has demonstrated its potential application to control enzyme-related seafood texture deterioration. Herefrom, it could be further applied to the freshwater fish processing and the effect of high pressure treatments on the activity of MBSP implicated in texture deterioration in myofibrils and crude enzyme extracts was evaluated. The inactivation kinetics of MBSP pressured from 200MPa to 500MPa at room temperature (20°C) were fitted first-order kinetics, The extent of enzyme inactivation was lower in silver carp myofibrils in comparison with the crude enzyme extracts from myofibrils showing a protective effect against the high pressure treatment. The effect of HHP on MBSP myofibrillar degradation shown by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) was associated with a corresponding decrease coincided with the elevated high pressure levels in intensity of myosin heavy chain (MHC). Dynamic rheological measurements indicated that high-pressure treatment exerted considerable influence on MBSP activities as well as proteins (mainly myofibrils), resulting in structural modifications and texture changes. In this study, 300MPa (≥10min) was the process condition (pressure and time) that caused apparent MBSP inactivation derived from the first order kinetic model and had the efficacy in controlling silver carp texture deterioration both verified by SDS-PAGE and dynamic rheological measurements.