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 degreesC) for 1 or 120 days ovine longissimus dors i muscle were studied by SDS-PAGE and ATPase activity assays. Muscles from two ovine 'double-purpose' (wool and meat production) breeds (Romney Marsh and Corriedale). and from one 'meat production' x 'double-purpose' crossbre ed (Ile de France x Romney Marsh) were compared. Myofibrils from unfrozen p ostrigor muscles showed similar SDS-PAGE patterns. Independently, of the ge notypes the troponin I (Tn-I) band gave a doublet after freezing and thawin g. 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 pre viously reported for bovine muscle. However, the T-max 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 mus cles. Only myofibrils fi-om Corriedale breed were affected frozen storage.