Changes in conformation and in sulfhydryl groups of actomyosin of tilapia (Orechromis niloticus) on hydrostatic pressure treatment

Actomyosin extracted from tilapia muscle was subjected to hydrostatic pressure treatment (50–300 MPa, 10–60 min, 4 °C) to investigate the changes in sulfhydryl groups and on conformation. Transmission electron microscopy showed that the structure of actomyosin was aggregated and disrupted above 100 MPa, and more regular network aggregates were observed as pressure increased. Moreover, pressurisation at 50 MPa for 10 min did not change actomyosin structures. Using SDS–PAGE analysis, molecules larger than the myosin heavy chain were observed when actomyosin was treated at and above 200 MPa. Below 200 MPa actomyosin formed aggregates, mainly with hydrogen bonds. Surface sulfhydryl group content of actomyosin increased with increased pressure, up to 250 MPa. However, total sulfhydryl group content of actomyosin decreased with increased pressure and time. According to this study, 200 MPa would be the critical pressure that induced actomyosin to form regular network structures.