A second mutant allele (V199I) at the PRKAG3 (RN) locus -: II.: Effect on colour characteristics of pork loin

Three alleles at the PRKAG3 (RN) locus that influence the glycogen content of pork were found to be segregating in Hampshire x Landrace crossbred pigs, RN-, rn(+) as well as second mutant allele V 1991 (here denoted rn*). The effect of these three alleles on ultimate pH, pigment content, internal reflectance (FOP), surface colour measured by tristimulus colorimetry (L*, a*, b*) and fractions of deoxymyoglobin (Mb), oxymyoglobin (MbO(2)) and metmyoglobin (MetMb) of pork loin was studied. Moreover, the effect of sex, entire male versus female pigs, on these traits was also analysed. The three PRKAG3 alleles affected ultimate pH, internal reflectance, colour and distribution of myoglobin derivatives of pork loin, while the pigment content was not influenced. Ultimate pH values of loins from the three genotypes were found to be in the order RN-/- genotypes < rn(+)/rn(+) genotype < rn(+)/ genotype rn(+)/rn(+) genotype. The internal reflectance in the loin was found to be in the order RN-/- genotypes <rn(+/)rn(+) genotype = rn(+)/rn(+) genotype = rn(+)/rn(+) genotype. The RN- allele was dominant resulting in higher redness (a* value) and yellowness (b* value), while the rn* allele tended to result in lower redness and yellowness compared with the rn* allele. The RN- allele was dominant over the rn* allele in lightness (L* value) giving a lighter colour. Surface colour differences were mainly explained by differences in the distribution of the myoglobin derivatives. Finally, surface lightness was higher and pigment content, redness and fraction of MbO(2) lower in loin from entire males compared with females. (C) 2003 Elsevier Ltd. All rights reserved.