LIBERATION OF PEPTIDES DURING MEAT STORAGE AND THEIR INTERACTION WITHPROTEINASE ACTIVITY

The content of nitrogenous material extracted in perchloric acid from kid longissimus lumborum (LL), semimembranosus (Sm) and triceps brachi i (TB) muscles increased 30% during storage for three weeks at 4 degre es C. The extract of fresh muscle contained a range of molecular sizes up to 13 kDa, the majority less than 4 kDa. The amount of the larger polypeptides ( > 4 kDa) extracted from meat decreased to 50% of its in itial level in meat stored for five days and to 20% after 25 days. The amount of intermediate sized peptides (1.9 to 4 kDa) remained largely constant throughout storage of meat of normal pH, whilst in meat of h igh ultimate pH, they showed a transitory increase during the first tw o weeks storage. Smaller size peptides increased with storage time; in creasing more slowly in meat of high ultimate pH. This time-dependent pH effect indicates a sequential autolysis involving neutral followed by acidic proteolytic and peptidic activity. Calpain from beef muscle degraded peptides in the extract and the extract acted as a competitor against a synthetic substrate. This implies that the in-situ autolysi s and tenderisation of meat post mortem could be reduced by peptide pr oducts. (C) 1998 Elsevier Science Ltd. All rights reserved.