Biochemical Variations in Salt Soluble Fractions of Ultrasonicated Actomyosin Isolated from Broiler Breast-Muscle

Abstract

Solubility and quality of actomyosin play crucial roles during storage and processing of a particular muscle type. We report here the effect of low intensity (20 kHz) ultrasonication on the solubility and some other biochemical properties of the actomyosin isolated from chicken breast muscle. Although there was an overall enhancement in the solubility of actomyosin during sonication, the major increase of~61.55% occurred at 0.2M NaCl after 10-12 min of exposure. The distinctive feature of sodium dodecyl sulphatepolyacrylamide gel electrophoretic (SDS-PAGE) profiles of this fraction was the presence of free or noninteracting actin in considerable amount. Even at higher salt concentrations (0.4 and 0.5M NaCl), the protein solubility was almost twice as high as that of the corresponding controls. At low salt concentrations (<0.3 M NaCl or KCl) where the protein solubility was high, Ca 2+-, K + (EDTA)-and Mg 2+-ATPase activities were low. However, a remarkable increase in each of the enzymatic activities occurred at the salt concentrations higher than 0.3 M. More importantly, the high level of Mg 2+-ATPase strongly indicated that actomyosin was reconstituted. The ultraviolet spectra also supported the reconstitution of actomyosin at high salt concentrations. These data suggested that ultrasonication caused conformational changes which modified properties of myosin and actin affecting the intermolecular relationships within actomyosin complex. The shift in the solubility and functional modifications of sonicated actomyosin provide some basis to explain the processing behavior of sonicated poultry meat. In addition, the low frequency sonication may be suggested as a non-destructive method to compare actomyosin extracted from various sources.