Influence of slaughter weight and stress gene genotype on the water-holding capacity and protein gel characteristics of three porcine muscles

The longissimus lumborum, gluteus medius, and the triceps brachii muscles from 40 animals were used to evaluate the effect of stress gene genotype (non-mutant, NN and mono-mutant, Nn) and live weight at slaughter (110kg and 140 kg) on the processing quality of fresh pork. The 45 minute and ultimate pH measurements did not differ between genotypes. Total percent protein was not different between samples taken from NN or Nn pigs, nor were there any differences in salt-soluble protein. The M. longissimus lumborum from Nn pigs possessed lower water-holding capacity values and lost greater amounts of water upon cooking. In addition, Nn pigs had lower subjective color and firmness scores which suggest a higher incidence of pale, soft and exudative pork. Slaughter weight did not affect total protein, salt-soluble protein, Minolta L*, a* and b* values or subjective color, firmness and marbling scores. Back fat thickness and loineye area increased as slaughter weight increased. Overall, this study suggested that Nn pigs have reduced water retention properties which may result in lower yields in processed meat items. Slaughter weight had limited effects on the processing quality of meat from NN or Nn pigs. There were no interactions of significance between stress gene genotype and slaughter weight, suggesting that the differences in muscle quality and functional properties between NN and Nn pigs are maintained over the slaughter weights used in this study.