Triose phosphate isomerase as an endogenous time-temperature integrator toverify adequacy of roast beef processing

Bovine muscle type had a large influence on the initial activity and heat s tability of triose phosphate isomerase (TPI). TPI activity in the round mus cles was more heat labile than in the chuck muscles. Residual TPI activity in bovine semimembranosus muscle was determined after cooking using adequat e and corresponding inadequate U.S. Department of Agriculture processing sc hedules. In both water bath and pilot oven studies, TPI activity was simila r in adequately processed beef (about 2 U/g) and increased when inadequatel y processed by reducing the holding time by 0.5 and 1.0 log at each tempera ture. Taken together, these results suggested that TPI could be used as an endogenous time-temperature indicator to verify processing adequacy of roas t beef if the muscle used in the product was known.