Thermal transition of collagen in ovine connective tissues

The thermal transition temperature (T(m)) of collagen in a range of muscle and non-muscle connective tissues from lambs, hoggets and mature sheep was measured by differential scanning calorimetry. The muscles selected were: semimembranosus (SM), semitendinosus (ST), biceps femoris (BF), Longissimus dorsi (LD) and psoas major (PM). Although the T(m) of intramuscular SM collagen from an aged ewe underwent no significant change with time post mortem, that of a 5-months-old lamb had dropped by 0·9°C after 2 days at 19°C. The epimysium of each muscle exhibited a higher T(m) than the corresponding intramuscular connective tissue. The LD and BF tendons each had a lower T(m) than corresponding intramuscular connective tissue but this was not true for the PM. Furthermore, the PM tendon generated an isometric tension more than five times that of the LD, BF or psoas minor tendons. This indicates that the PM tendon is richer in heatstable crosslinks than any of the other tendons investigated. In all tissues, except the liver capsule, there was an increase in T(m) with animal age. However, the rate of change T(m) varied from one tissue to another. For example, the SM intramuscular collagen matured at an earlier age than that of other muscles, the PM being slowest to mature. In keeping with the changes in T(m) values, the Warner-Bratzler peak force of ST muscles increased markedly in older sheep, but there was no significant difference in peak force of SM muscles between lambs, hoggets and mature sheep.