Abstract
Tenderizing effects of kiwifruit (Hayward, New Zealand) protease on beef shank were studied. Some pieces of the shank were incubated at 37°C for 1 hour with homogenate of kiwifruit (piece A), with the homogenate inactivated by heating (piece B) or without any homogenate (piece C), then raw or inactivated homogenate was taken away and the pieces were boiled for 0.5 - 2 hours, It was conthat piece A boiled for 0.5 or 1 hour was softer significantly than piece C boiled for 0.5 or 1 hour, respectively, judged by Scheffe pair test. However, there were not significant differences in softness between pieces A and B boiled for 1 hour, or pieces B and C boiled for 1 hour by sensory paired difference test. So it was assumed that any thermostable factor might also be concerned on the tenderization. Furthermore, softness of piece C boiled for 1 hour was not significantly different with that of piece A boiled for 0.5 hour by the Scheffe test. Levels of f ormol nitrogen and extractive in soup stock prepared from piece A were higher significantly than those in that prepared from piece C. Quantity of formol nitrogen liberated from piece A was equal to that from the piece incubated with the raw homogenate at 7°C for 15 hours. It was also found by formol titration that rate of the digestion of shank, which had previously frozen and then thawed, by the kiwifruit homogenate was faster than that of raw shank and that the rate of stroma prepared from the shank was slower than that of the prepared myofibril or the homogenate of raw shank. Mallory's stain on boiled piece A gave some different reaction microscopically with that on boiled piece C.
