Colour Characteristics of Fresh Pork

Lindahl, G. 2005. Colour characteristics of fresh pork. Doctor’s dissertation. ISSN 1652-6880, ISBN 91-576-7042-0 The objective of the present thesis was to obtain more fundamental understanding of the mechanisms for variations in colour and colour stability of fresh pork. The effects of breed and genotype, including Duroc, Hampshire (three RN alleles), Landrace and Yorkshire pigs, were studied. Furthermore, effects of strategic feeding with creatine, pre-slaughter treatment, slaughter procedure and carcass cooling on muscle metabolism and ultimate colour and colour stability were studied. It was concluded that the early progress in post mortem temperature and pH decline affect the colour of pork independent of whether this is triggered by variations in genotype, feed-induced changes, pre-slaughter stress or cooling rate. The level of oxymyoglobin was shown to be more important for the colour of pork during retail display, than the level of metmyoglobin. A high level of oxymyoglobin preserves high redness despite of oxidation to metmyoglobin. Ageing of pork for a week increased the ability of pork to stimulate oxygenation of deoxymyoglobin to oxymyoglobin, i.e. blooming, without compromising the colour stability during four days of subsequent retail display. Hence, ageing results in lighter, redder and more yellow pork colour. It was further concluded that genetics giving rise to variation in the colour of pork is related to differences in pigment content and in muscle metabolism. The latter influences the redox status of the muscle and the activity of oxygen-consuming and metmyoglobinreducing enzymes and accordingly the relative proportion of the myoglobin species. The colour of pork from Landrace pigs was generally lighter, redder and more yellow than pork from Duroc pigs due to higher level of oxymyoglobin at the meat surface, i.e. more intense blooming. The colour of pork from Hampshire pigs was highly related to the RN genotype. Pork from carriers of the RN− allele was generally lighter, redder and more yellow than that from non-carriers of the RN− allele, and the rn* (V199I) allele tended to decrease redness and yellowness.