Thermal stability of connective tissue from porcine muscles

Connective tissue of three porcine muscles (M. infraspinatus, IS; M. longissimus dorsi, LD; M. semimembranosus, SM) from 27 animals [populations A (n=13, reared in Ireland) and B (n=14, reared in Finland)] was studied by measuring the collagen content, collagen solubility and thermal shrinkage temperature of the connective tissue. Colour and pH were also determined. Collagen solubility was highest in IS (p<0.05) and lowest in SM (p<0.05) although no difference between LD and SM was found in population B. The onset and peak temperatures of thermal shrinkage (T(o) and T(p)) were highest in IS (p<0.05). The lowest T(o) and T(p) were found in SM from population B whereas no differences were seen between LD and SM muscles in population A. It was concluded that the thermal stability of the connective tissue in the three porcine muscles differ. IS, as a dark muscle has high thermal shrinkage temperatures and high collagen solubilities in comparison to the lighter LD and SM muscles which have lower thermal shrinkage temperatures and collagen solubilities. Collagen contents were highest in IS and lowest in LD.     

Effect of muscle type and cooking temperature on liver‐like off‐flavour of five beef chuck muscles

Steaks (1.9 cm thick) from the US Department of Agriculture (USDA) Select grade beef chuck muscles (Infraspinatus, Longissimus dorsi, Serratus ventralis, Supraspinatus and Terres major) were cooked to two temperatures commonly applied in US restaurants (71 °C and 82 °C) and evaluated for liver‐like off‐flavour by trained panel. Pigment content of raw muscles were determined to establish its effect on liver‐like off‐flavour. Mean myoglobin content of Serratus (9.26 mg g^?1) was significantly lower than other beef chuck muscles analysed in this study. Infraspinatus had highest (P < 0.05) mean liver flavour of 2.08 where other muscles had <2. Rancid flavour was slightly but significantly increased from 1.34 to 1.58 as internal cook temperature increased from 71 °C to 82 °C; however mean thiobarbituric acid (TBA) values were not affected by cooking temperature. Infraspinatus had small but significant incidence of liver‐like off‐flavour. Cooking temperature had a clear impact on rancidity as evaluated by trained panel but no direct impact on liver‐like off flavour was observed.