Effect of dietary variation,with respect to energy and crude protein levels,on the oxidative rancidity exhibited by frozen porcine muscles

The phenomenon of oxidative rancidity exhibited by porcine muscle tissue when held under conditions of frozen storage is influenced by a number of factors. These factors determine the variability exhibited by different muscles with respect to oxidative rancidity. One such factor which is intimately concerned with the above phenomenon is the level of constituent polyunsaturated fatty acids of the intramuscular lipids. In the case of the intramuscular triglyceride fraction, the level of constituent polyunsaturated fatty acids can be modified by dietary means. An experiment is described in which the effect of different diets on the tendency of minced frozen porcine muscle to undergo oxidation was investigated. The particular diets used varied in energy and protein levels and were typical of the kinds of diets used to improve the growth rates and commercial carcase quality of pigs. The results obtained indicated that the particular diets used had little effect on the fatty acid content of the porcine muscle triglycerides and none on that of the phospholipids. It was in the latter fraction that oxidation was mainly exhibited. The major factor influencing the susceptibility of minced frozen porcine muscle to undergo oxidative rancidity, within the dietary limits of the experiment described, was found to be the ultimate (24 h post mortem) pH level of the muscle concerned.