The thermal properties of titin isolated from porcine and bovine longissimus muscles were investigated by differential scanning calorimetry in the temperature range from 20 to 100 °C. A single peak with average maximum temperatures of 75.6 and 78.4 °C characterized porcine and bovine titin denaturation, respectively. The peaks were much broader than those from the other major muscle proteins. Titin denaturation enthalpy values (1.6-2.6 J/g) were only about half those of whole meat and also lower than those previously determined for myosin, actin, or collagen. The relatively high titin denaturation temperature suggests that it may be partially responsible for meat toughening when muscle tissue is heated above 60 °C.