Physicochemical characteristics of muscles from free-range reared pigs.

Abstract

In this study we analysed the chemical composition and physical characteristics of four muscles from Alentejano (AL) pigs, m. Biceps femoris (BF), m. Semimembranosus (SM), m. Longissimus dorsi (LD), and m. Psoas major (PM). Castrated male and female AL pigs allocated to an outdoor rearing area and fed a commercial diet offered at 85% estimated ad libitum consumption, were slaughtered at ~105 kg live weight. BF, SM, LD, and PM individual samples were obtained from the left side of each chilled carcass. Significant differences were mainly found on the chemical composition and colour of the muscles. LD muscle presented the highest amount of intramuscular fat (5.9%), and SM the lowest (3.4%). These differences agree with the lower moisture content on LD (69.2%) and higher content on SM (73.1%). The myoglobin content was higher on PM (3.81 mg/g), followed by SM (2.74), BF (2.30), and LD muscle (1.21). These myoglobin contents explain the obtained physical colour measures: the PM muscle presented the higher (P<0.001) CIE a* and C* values (18.8 and 20.2, respectively), followed by SM (16.0 and 17.3), BF (15.5 and 16.4), and LD (12.0 and 13.1) muscles. The content of total collagen was higher (P<0.001) on BF and SM muscles (1.51 and 1.45 mg/g, respectively), and lower on LD and PM muscles (0.96 and 1.01). The soluble fraction of collagen did not differ among muscles, varying between 0.16 (LD) and 0.21 mg/g (SM). These results indicate that there are important differences between muscles and that these differences will have impact on the sensorial quality (e.g. colour and texture/toughness). Thus, the PM muscle was the most reddish/attractive muscle, with lower collagen content, and the LD muscle had a pale colour, the lower collagen content and the higher content of intramuscular fat. These parameters agree with the higher commercial value of the LD muscle, related with higher sensorial properties (toughness and juiciness).