A tenderizer mixture consisting of partially purified papain and oryzae protease was used to tenderize two cuts of
beef meat; namely, bottom round (Bicepesfemoris) ,and sirloin (Longissimusdorsi) , taken from old aged animal after
24 hr of slaughter. Sensory and chemical methods were used for the assessment of meat quality. Highly significant
difference was detected between the scores for the tenderized cuts and the control, with no detectable difference for
flavour. Freezing the enzyme treated meat and thawing before cooking, reduced the cooking time. Positive correlation
coefficient was obtained between tenderness scores and TCA-soluble nitrogen. Generally, TCA-soluble nitrogen
increased by increasing the enzyme concentration. Yet, the results revealed that the amount and the source of the used
enzyme, must be selected to avoid toughness or mushiness due to under or over tenderization of the meat. Each of the
partially purified papain and oryzae protease, as well as a mixture of the two preparations was used for the histological
study. The study necessitated the use of relatively high enzyme concentration (4%), than those used for proper
tenderization being 0.0025 and 0.005%. That is to facilitate the demonstration of even the minor changes of the tissue
muscle fibers and connective tissues. The muscle fibers, bundles of fibers, nuclei at periphery of the fibers, fat cells,
connective tissues, perimysium collagen, sarcolemma which envelope the muscle were apparent in both of the stained
cross and longitudinal sections. The muscle histological structures were markedly affected, to various degrees by the
enzymatic tenderization. The effect of papain was more pronounced than that of oryzae proteases, particularly upon
cooking.