The influence of diets supplemented with CLA, selenium, and vitamin E, with or without animal protein, on the quality of pork from female pigs

¹ Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand
² New Zealand Institute for Crop and Food Research, Food Industry Science Centre, Palmerston North, New Zealand

^* To whom correspondence should be addressed. E-mail: R.Purchas{at}massey.ac.nz.

	Abstract

Pork from the longissimus (LM) and semimembranosus (SM) muscles of 59 female Duroc-cross pigs with a mean carcass weight of 80.1 kg (SD = 3.2) were assessed for quality. The pigs were grown on diets containing either animal and plant products (the animal group) or plant products only (the plant group), with or without a supplement (0.31% of the diet) containing extra CLA, selenium and vitamin E. The 45-min postmortem pH of LM was unaffected by dietary treatment (mean 6.44, SD = 0.21), but the ultimate pH (pHu) was lower for the supplemented animal group for both muscles within the animal group (P < 0.04). Water-holding capacity in terms of drip loss for SM and expressed juice levels for LM, but not cooking loss, was also lower for the supplemented animal group (P < 0.01), but this difference was greatly reduced after adjustment to a constant pHu (P < 0.07). Warner-Bratzler shear force (WBSF) values were higher for the plant group for LM only (P < 0.05), both before and after pHu adjustment. Differences between dietary treatment groups for color (L*, a* and b*) were small and seldom significant either before or after pHu adjustment. Sensory assessment of LM samples (with 5% subcutaneous fat added) from 32 pigs (8 per group) for eight odor notes and eleven flavor notes by a trained analytical sensory panel of 13 people revealed no differences between the groups except that the percentage of instances when a rancid odor was detected was higher for the supplemented plant group compared with the control plant group (25% vs 12%). Differences (P < 0.001) were shown between the muscles such that, relative to SM, LM had lower pHu values, higher drip losses, higher WBSF values, higher L* values, and lower chroma values, but similar levels of cooking loss. It is concluded that the dietary treatments imposed to improve the nutritional value of pork had some effects on certain meat quality parameters, but that the overall effects on appearance and palatability were small and unlikely to be of practical importance.

Key Words: Pork quality, Flavor, Odor, Pork color, Water-holding capacity, Tenderness