Gelation and Thermal Transitions in Post‐Rigor Turkey Myosin/Actomyosin Suspensions

Abstract

A myosin/actomyosin mixture (MAM), actomyosin and myosin were isolated from post-rigor turkey. Rheological properties of MAM gels were determined by uniaxial compression. Breast MAM formed gels which were stable at lower protein concentrations (10 and 15 mg/mL) than thigh MAM (20 and 25 mg/mL). Differential scanning calorimetry (DSC) and a fluorescent hydrophobic probe, 8-anilino-l-napthalene sulfonate (ANS), were used to study thermal transitions. One DSC peak was observed in breast and thigh MAM. ANS thermograms showed that thigh actomyosin had a greater transition temperature (Tr) (518°C) than breast actomyosin (49.7"C). The ANS Tr was 48°C for both myosins. The difference in gelation appeared to be associated with protein-protein interactions.

Gelation of Turkey Breast and Thigh Myofibrils: Changes During Isolation of Myofibrils

“…This contrasted with observations reported on myofibrillar proteins, where those isolated from white (breast) meat had greater fracture stress and strain (Foegeding, 1987;Dudziak et al, 1988) and puncture strength (Xiong and Brekke, 1991) than those from dark (leg or thigh) meat. A possible reason for the discrepancies is that normal pH of dark meat (-6.2), being higher than white meat (-5.6), is more favorable for molecular interactions which cause gelation (Amato et al, 1989).…”

“…Results showed no difference in shear stress or shear strain values of thermally induced breast and thigh myofibril gels. Gel fracture properties have been related to relative amounts of myosin and actomyosin in myofibrillar protein fractions (Dudziak et al, 1988;Foegeding et al, 1991). Myosin/actomyosin (MAM) gels (10-25 mg/ml) formed at pH 7.0 from breast meat proteins have higher shear stress and strain than similar gels from thigh meat proteins (Dudziak et al, 1988).…”

“…In the EDTA and subsequent steps, ground breast or thigh meat was chopped in the presence of 20 mM EDTA buffer. The chopping, centrifugation and decanting of supernatant allowed removal of water-soluble proteins and other muscle components (Knight and Trinick, 1982;Dudziak and Foegeding, 1988). The RIGOR step involved a series of homogenizations and centrifugations in the presence of a rigor buffer.…”

“…Adjusting pH of cornminuted breast meat to that of thigh (pH 6.4) caused shear stress of gels to equal thigh values and increased shear strain to a value significantly (P < 0.05) greater than thigh gels. This pH effect did not account for fracture property differences between breast and thigh myosin-actomyosin gels (Dudziak et al, 1988).…”

“…Most investigations concerning gelation mechanisms and gelling properties on processed meat products have been on isolated myofibrillar proteins or cornminuted meats (Ishioroshi et al, 1979;Acton et al, 1983;Asghar et al, 1984;Foegeding, 1987;Dudziak et al, 1988;Smith et al, 1988;Daum-Thunberg et al, 1992).…”