Influence of rearing conditions and crossbreeding on muscle color in Iberian pigs

The effects of pig crossbreeding (Iberian versus Iberian x Duroc 50%) and rearing conditions (outdoors versus indoors) on muscle fiber composition, myoglobin content and objective muscle color in biceps femoris and tibialis cranealis muscles have been studied. Muscle fibers were identified as types I, IIA, IIB, oxidative IIB and IIC and the proportion of each fiber type was determined by a computerized image analysis. Color co-ordinates L*, a*, and b* were measured and both chroma (C*) and hue angle (h degrees) were calculated. Myoglobin content and chroma value were significantly higher in tibialis cranealis muscle than in biceps femoris muscle (p less than or equal to 0.001), whereas the former muscle showed the lowest lightness and hue angle values (p less than or equal to 0.001). Moreover,tibialis cranealis muscle exhibited a higher total proportion of oxidative fibers, types I, IIA and IIBx (p less than or equal to 0.05), and a lower fat content than did biceps femoris muscle (p less than or equal to 0.001). The muscles of pigs reared outdoors tended to show a higher percentage of oxidative fibers (type I) than did muscles from indoor reared pigs, although not to a significant extent. Rearing conditions significantly affected color, muscles from outdoor reared pigs exhibiting higher lightness (L*), chroma (C*) and hue angle (h degrees) than muscles from indoor reared pigs. However, neither the crossbreeding nor the rearing conditions showed a significant influence on myoglobin concentration of muscles.