Biochemical Properties of Myofibrils from Frozen Longissimus Dorsi Muscle of Three Lamb Genotypes

The protein composition and biochemical properties of myofibrils from fresh and frozen stored (-30 °C) for 1 or 120 days ovine longissimus dorsi muscle were studied by SDS-PAGE and ATPase activity assays. Muscles from two ovine `double-purposeʹ (wool and meat production) breeds (Romney Marsh and Corriedale), and from one `meat productionʹ×`double-purposeʹ crossbreed (Ile de France×Romney Marsh) were compared. Myofibrils from unfrozen postrigor muscles showed similar SDS-PAGE patterns. Independently of the genotypes the troponin I (Tn-I) band gave a doublet after freezing and thawing. In addition, a significant (P<0.01) increase in the relative areas of both 30- and 32-kDa bands was observed. The genotypes differed with regard to Mg2+- and Ca2+ATPase activities of myofibrils during frozen storage of the muscles. Differential Scanning Calorimetry (DSC) studies demonstrated that the whole ovine muscle had similar thermogram profiles than those previously reported for bovine muscle. However, the Tmax corresponding to the first endothermal transitions in the muscle of two ovine genotypes showed a trend to higher values compared to those formerly reported for bovine muscles. Only myofibrils from Corriedale breed were affected by frozen storage.