The mechanism of high pressure-induced gels of rabbit myosin

Rabbit myosin (20 mg/mL of 0.6 M NaCl, pH 6.5) was subjected to various pressures (100–400 MPa) at 20 °C for 10 min to investigate pressure-induced gel mechanism by measurements of protein surface hydrophobicity, sulfhydryl contents, molecular size by native polyacrylamide gel electrophoresis, ultra-structure using SEM, and viscoelastic properties by dynamic rheology. Surface hydrophobicity and sulfhydryl groups had little increase at 100 and 200 MPa, but had significant increase at 300 and 400 MPa. Ultra-structure revealed that gels below 200 MPa were filament structure with many small cavities, while gels upon 300 MPa were globular aggregates with big cavities. Dynamic rheological measurements indicated that gels were formed at 400 MPa. Mechanism of myosin gel formation in pressure treatment was that myosin was unfolded, following the exposure of hydrophobic and buried sulfhydryl groups, then was denatured (electrophoresis showed the heavy chain became very weak) and associated to form gels. In recent years, high pressure treatment of food has received interest as an alternative to heat treatment for gel formation. Gel-type meat products of high pressure processing are still not commercialized. This is basically due to lack of information about high pressure-induced gel. Myosin is the protein responsible for the gelling capacity of muscle systems. The processing characteristics of gels treated by high pressure were improved. The results of this experiment showed that myosin denatured and formed gels at pressure 400 MPa holding for 10 min. This information will help industry to adopt high pressure to produce meat products.