Gelation of Chicken Muscle Myofibrillar Proteins Treated with Protease Inhibitors and Phosphates

Gelation of chicken pectoralis muscle myofibrils treated with soybean trypsin inhibitor, leupeptin, antipain, egg white, ethylenediaminetetraacetic acid, and ortho- (P_i), pyro- (PP_i), tripoly- (TPP), or hexametaphosphate (HMP) was studied by dynamic rheological and differential scanning calori-metrical measurements at pH 6.0. Most myofibril samples exhibited two distinctive thermal transitions and a major rheological transition during heating from 25 to 80 °C. The abrupt loss of shear moduli upon heating from 50 to 55 °C was not prevented by protease inhibitors, indicating that gel weakening was unlikely caused by common endogenous proteases. PP_i, which destabilized myosin, interfered with myofibril gelation. TPP, which also destabilized myosin, markedly improved myofibril gelation in 0.3 or 0.4 M NaCl but decreased the gelling ability in 0.6 M NaCl. HMP, showing no effect on myosin denaturation, increased shear moduli of myofibril gels. The results may partially explain variations in functionality of poultry meat formulated with different phosphates when various levels of NaCl are used.