Influence of rearing conditions and crossbreeding on muscle color in Iberian pigs Influencia de las condiciones de crianza y del cruce en el color de los músculos de cerdos Ibéricos

The effects of pig crossbreeding (Iberian versus Iberian x Duroc 50%) and rearing conditions (out doors versus indoors) on muscle fiber composition, myoglobin content and objective muscle color in biceps femoris and tibialis crancalis 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 computer ized image analysis. Color co-ordinates L*, a*, and b* were measured and both chroma ( C*) and hue angle ( h°) were calculated. Myoglobin content and chroma value were significantly higher in tibialis cranealis muscle than in biceps femoris muscle ( p ≤ 0.001), whereas the former muscle showed the lowest lightness and hue angle values ( p ≤ 0.001). Moreover, tibialis cranealis muscle exhibited a higher total proportion of oxidative fibers, types I, IIA and IIBx ( p ≤ 0.05), and a lower fat content than did biceps femoris muscle ( p ≤ 0.001). The muscles of pigs reared outdoors tended to show a higher per centage of oxidative fibers (type I) than did muscles from indoor reared pigs, although not to a sig nificant extent. Rearing conditions significantly affected color, muscles from outdoor reared pigs ex hibiting higher lightness ( L*), chroma ( C*) and hue angle ( h°) than muscles from indoor reared pigs. However, neither the crossbreeding nor the rearing conditions showed a significant influence on myoglobin concentration of muscles.