title: The fate of the large proteins of the myofibril during tenderising treatments.
abstract: Changes in the large structural proteins of the myofibril, during treatments which affect tenderness, have been followed using SDS-PAG electrophoresis. Despite the known decay of gap filaments during ageing, and the identification of connectin as their substance, connectin survives prolonged ageing at 15°C (although it succumbs at temperatures at which it denatures). Cold shortening or stretching of muscle does not affect autolysis, except in the prolonged ageing of stretched samples, where myosin 'heads' are apparently detached due to their greater accessibility to proteases. The only two changes on the same time scale as tenderisation are the disappearance of nebulin and an increase in a protein lying between connectin and nebulin on the gels. The evidence for nebulin as the N(2)-line protein is questionable, and it is proposed that it may instead be a component of the G-filaments, necessary for their stability. In pressure-heat (P-H) treatment at 50 or 55°C, which reduces yield point rather than shear force, connectin survives, while nebulin is partly destroyed. A tenderising P-H treatment at 60°C degrades both. Cooking to various degrees apparently causes a random splitting of connectin, revealed as a smear down the gels. After cooking at 80°C a little of the original band survives, while most of the smear represents material with a molecular weight above half a million, and should therefore still be capable of contributing to structural strength. Prior tenderising treatments have little effect on gels derived from material cooked at 80°C, although what remains of the sharp connectin band in cooked controls disappears in aged or P-H treated samples.
authors: Meat Industry Research Institute of New Zealand, PO Box 617, Hamilton, New Zealand.
authors: R H
authors: RH
authors: Locker
authors: D J
authors: DJ
authors: Wild