Thermal transitions of natural actomyosin from poultry breast and thigh tissues

Natural actomyosin was isolated from broiler breast and thigh tissues, characterized by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and examined for thermal transitions (Tm) during heat-induced aggregation. Electrophoresis showed some variation in the quantity of each subunit protein present between the tissue actomyosins and, with Amido Black staining, yielded actin to myosin molar ratios of 5.71 and 6.33 for breast and thigh natural actomyosins, respectively. The heat-induced initiation of protein to protein interactions occurred at 30 to 31 C for actomyosin of breast tissue and at 42 to 44 C for actomyosin of thigh tissue. Two distinct thermal transitions were found for each actomyosin. Derivative curves from the plot of differential change in optical density or absorbance (A) as a function of temperature (T) (dA/dT) between 28 C and 70 C showed Tm1 at 49.2 C and Tm2 at 60.2 C for breast actomyosin with corresponding values of Tm at 52.6 C and 57.9 C for thigh actomyosin. The interval between Tm1 and Tm2 (delta Tm) for thigh actomyosin (5.3 C) was less than that of breast actomyosin (11.0 C). This result suggests that less thermal energy is required for aggregation of actomyosin from thigh tissue. The differences in thermal characteristics between the two actomyosins may be related to differences observed in heat-processed products prepared from breast and thigh tissues.