Effect of pre-slaughter physiological conditions on the oxidative stability of colour and lipid during chill storage of pork

The physiological condition of the live animal was found to significantly a ffect colour, lipid oxidation and water holding capacity of chill stored po rk chops (M. Longissimus dorsi) in a study, where various pre-slaughter con ditions were achieved by the following four treatments: (A) control; (B) su bjected to treadmill exercise immediately prior to stunning; (C) given epin ephrine injection 15 h prior to slaughter; and (D) given epinephrine inject ion 15 h before slaughter and further subjected to treadmill exercise immed iately before stunning. The treatments resulted in variations in energy met abolites (glycogen, lactate, creatine phosphate, ATP) and ultimate pH (pH,) , with the lowest pH, in chops from treatments A and B, and in significantl y different tristimulus colour L*-, a*- and b*-parameters, although the eff ect of treatment on colour was not consistent during the chill storage peri od df 6 days. Overall, chops from treatments A and B had significantly high er L*- and b*-values (were paler and less blue) than chops from C and D dur ing storage under conditions typical for retail trade. The initial ah-value s were higher (redder) in chops from treatments A and B, but the colour, as judged by the a*-values, was less stable in meat from these treatments com pared with treatments C and D. Lipid oxidation, evaluated by thiobarbituric acid reactive substances (TBARS) in the fresh meat, and drip loss, measure d after 6 days of storage, were both significantly higher in chops from tre atments A and B compared to chops obtained from treatments C and D. Statist ical analysis relating the pH and the level of various energy metabolites p ost-mortem in the individual animals to the measured quality parameters, re vealed that pH, was the most important factor affecting product quality. In conclusion, over all product quality depends on obtaining a pH, in the nar row range where both meat quality parameters such as colour, lipid oxidatio n and drip loss as well as microbiological aspects have to be considered. ( C) 2001 Elsevier Science Ltd. All rights reserved.