The relative effects of an aspartic proteinase (AP) and papain on meat proteins and beef tenderness were evaluated by measuring release of hydroxyproline in collagen, and breakdown of myofibrillar proteins. Tenderness was objectively measured by Warner-Bratzler shear. AP showed self-limiting hydrolysis of myofibrillar proteins resulting in 25 to 30% improvement in meat tenderness and was not adversely affected by pH, salt, phosphate, and ascorbate concentrations often encountered in meat processing. Like papain, its tenderizing effect was expressed primarily during cooking and caused no significant changes (p . 0.05) in tenderness during frozen or refrigerated storage. It was also inactivated at cooking temperatures in excess of 60°C, therefore eliminating any undesirable side effects that may be associated with residual protease activity.

Staphylococcus aureus strain V8 protease is a serine endopeptidase which cleaves peptide bonds at the carboxyl side of Glu and Asp. Specific cleavage at Glu has previously been achieved in ammonium bicarbonate whereas in sodium phosphate cleavage at both Glu and Asp was observed. However, it is shown here that bicarbonate does not restrict the specificity to Glu‐X bonds, it simply inhibits the enzyme. The degradation of a mixture of oxidized insulin and glucagon proceeds similarly in the two buffers, although faster in phosphate.