THE INFLUENCE OF HIGH POSTMORTEM TEMPERATURE AND DIFFERING ULTIMATE PH ON THE COURSE OF RIGOR AND AGING IN PIG LONGISSIMUS-DORSI MUSCLE

This study was performed in order to assess the effect of temperature and differing ultimate pH (pH(u), 24 h post mortem) on the development of rigor mortis in pig Longissimus dorsi muscle. The rigor developmen t (isometric tension and shortening) was measured continuously during the first 24 h post mortem, using an apparatus wherein muscle strips w ere held at constant temperatures of 12 or 35-degrees-C pH(u) was mani pulated by adrenaline injections preslaughter. The rates of pH fall, a denosine triphosphate (A TP) and creatine phosphate (CP) breakdown wer e markedly increased al 35-degrees-C compared to 12-degrees-C For both temperatures, no delay phase was observed with regard to the developm ent of shortening. Rigor resulted in higher maximum isometric tension and shortening and in shorter time needed to reach maximum values at 3 5-degrees-C than at 12-degrees-C The results are discussed in connecti on with pH, ATP and CP data. The extent of ageing from 2 to 4 days pos t mortem, estimated through myofibrillar length determinations, was hi gher for 12-degrees-C than for 35-degrees-C. pH(u) affected significan tly most of the traits under study, but its effect depended in some ca ses upon the rigor temperature. At 12-degrees-C, the traits related to the kinetics of rigor development were significantly affected by pH(u ), but this was not the case at 35-degrees-C. Maximum isometric tensio n was significantly related to pH(u) at 35-degrees-C (r = 0.86, P < 0. 001), but such a relationship was not found at 12-degrees-C Myofibrill ar lengths were significantly affected by pH(u), but in an opposite ma nner from one temperature to another. A positive relationship was foun d at 12-degrees-C and a negative one at 35-degrees-C. These results il lustrate the importance of the interaction between the extent of pH fa ll and temperature with regard to post-mortem changes in pig muscle.