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Meat tenderness is one of the most important quality criteria when evaluating results of cooking conditions. Changes in tenderness and weight losses of heat-treated meat (semitendinosus muscle) for different time-temperacure Combinations were analyzed; the relationship between protein denaturation and textural changes was studied.Heat treatments of meat samples (I .5 cm in diameter, 2 cm long) were perjormed in a thermostatic bath in the 60-9OC range. Maximum heating times were 180 min. Meat hardness was determined by Warner-Bratzler measurements using an lnstron testing machine. Protein denaturation was followed by Differential Scanning Calorimetry (DSC) analyzing peaks for myosin (1 and Il), sarcoplasmatic proteins and collagen (11) and actin (1Il).Between 60 and 64C, hardness decreased with cooking time until reaching the lowest asymptotic values. This was related to protein denaturation of peak 1 and Il. Between 66 and 68C, hardness decreased at first but increased later due to actin denaturation; at the temperatures 81 and 90Cno modifications were observed and hardness remained at its higher values.The kinetic model proposed fit the experimental results satisfactorily. Activation energies of tenderizing and toughening processes are similar to those of protein denaturation of peak 11 and Ill. Weight losses due to cooking were also modelled increasing through the entire temperature range.