Progressive changes in Warner-Bratzler shear values of meat cores and in dimensions and integrity of muscle fibers from beef semitendinosus cores heated in tubes in a water bath to simulate oven roasting of top round roasts at 93 and 149°C to endpoint temperatures of 40, 50, 60 and 70°C were evaluated. Slower heating and higher endpoint temperatures resulted in greater cooking losses. Warner-Bratzler shear values and muscle fiber diameters decreased from 40 to 50 to 60°C. Sarcomere length of muscle fibers decreased from 60 to 70°C. Muscle fibers disintegrated as internal temperature increased. Fiber disintegration was greater at the faster rate of heating for cores heated to 60°C than at the slower rate. A faster rate of heat penetration might result in greater degradation of muscle fibers at a lower temperature. An increase in fiber disintegration with heating of cores from 60 to 70°C suggested an increase in tenderness, but changes in shear values were not apparent in this temperature range. It appears that other factors oppose the tenderizing effect of increased disintegration of muscle fibers at higher temperatures.

Beef rib cuts were oven roasted at 107° and 163°C. to end points of 60°, 70°, and 77°C. Cooking losses, tenderness, and other sensory properties were evaluated and related to histological changes in muscle components. Cooking times were longer and cooking losses usually lower at 107°C. than at 163°C. As end point temperature increased, cooking time and cooking loss increased and juiciness decreased. Shear values for cuts heated to end points of 70° and 77°C. at 107°C. were lower than for all other heat treatments. Roasts cooked at 107°C. to each end point and those cooked at 163°C. to 60°C. received higher tenderness scores than did all other heat treatments. Muscle fiber diameter decreased approximately the same extent with heating at either oven temperature. Fiber diameter decreased as end point temperature increased from 60° to 70°C., but diameter increased between 70° and 77°C. Quantity of collagenous connective tissue appeared to be greater in cuts heated at 163°C. to 60°, 70°, and 77°C. and at 107°C. to 70°C. than at other heat treatments. With increasing oven and end point temperatures, collagenous tissue changed from a banded to a granular appearance and fat became dispersed in the perimysial and endomysial collagenous tissue.

Effects of end point temperature in unheated (10°C) muscle and muscle heated (dry heat, 176°C) to 25, 35, 45, 55 and 65°C on moisture measured by selected methods, Warner-Bratzler shear values, and pH values of breasts and thigh-legs from tom turkeys were investigated. Also, rate of heat penetration, temperature differentials, and post-oven temperatureincreases of breasts and thigh-legs were noted. Increase in temperature in each of three positions in breasts and thigh-legs tended to follow a similar pattern for all pieces of the same type.End point temperature significantly (P= 0.05) affected anterior-posterior, and posterior-mid-position temperature differentials in breasts, but affected only distalmid-position temperature differential in thigh-legs. Post-oven temperature increases decreased with increase in end point temperature, and were significantly (P = 0.05) different between 35 and 45°C for breasts, and for all temperatures except between 4.5 and 55°C for thigh-legs.

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