Evidence of Proteolytic Activity and Its Effect on Gelation of Myofibrillar Protein Concentrate from Bovine Cardiac Muscle

To explore the impact of endogenous proteases on the gelation properties of beef heart surimi, the surimi samples were incubated at different temperatures. Maximum (4.8 N) and minimum (3.3 N) gel strengths were produced by surimi sols preincubated at 60 and 50°C, respectively. Preincubation at 60°C as well as slow linear heating also produced gels with the highest storage modulus and water-holding capacity. Proteolytic activity with an optimum pH of 5.0 and temperature close to 50°C was discovered. Addition of protease inhibitors, particularly bovine plasma powder, reduced the extent of gel weakening caused by the proteases and, concomitantly, enhanced the water-holding capacity of the surimi gel. SDS-PAGE showed that in the absence of protease inhibitors, myosin was partially hydrolyzed and a 130 kDa polypeptide formed during preincubation at 50°C. Bovine plasma powder and egg white inhibited the formation of the new polypeptide.