| Budget Amount *help |
¥5,400,000 (Direct Cost: ¥5,400,000)
Fiscal Year 1989: ¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 1988: ¥2,700,000 (Direct Cost: ¥2,700,000)
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| Research Abstract |
This study was undertaken to elucidate the mechanism controlling the accumulation of 5'-GMP in Shiitake mushroom during the cooking.
(1) The distribution of RNA, nuclease and phosphatase in Shiitake and these changes during the growth were examined. The concentration on RNA, which is richer in cap part than in stalk part, decreased during the growth. At the second half of growth period, the concentration in cap part was in the following order: gill > upper surface > middle layer. Nuclease and phosphatase activities in cap part gradually decreased during the growth. The distribution of nuclease was localized to gill and that of phosphatase to upper surface.
(2) Changes of RNA and the related compounds in Shiitake during the cooking were examined. When Shiitake homogenate was incubated at 60ﾟC, the amount of 5'-nucleotides rapidly increase passed through a maximum within about 5min, and then fell off. On the other hand, when whole Shiitake was soaked in water at 60ﾟC, the amount of 5'-nucleotides in Shiitake tissue changed in the same manner as in the homogenate, but that in soaking water rapidly increased, reached a maximum in 15min, and then scarcely decreased. When whole Shiitake soaked in water was cooked at a constant heating rate, the amount of 5'-nucleotides increased rapidly at 60-70ﾟC, and reached a constant level at 80ﾟC.
From these observations, it is suggested that, as well as faster heat inactivation of phosphatase than nuclease, the diffusion of 5'-nucleotides formed at a restricted part of Shiitake tissue, to soaking water or to some parts of Shiitake tissue where is poor in phosphatase activity, may play a key role in the accumulation of 5'-nucleotides during the cooking of Shiitake.
(3) Of drying conditions and cooking conditions of Shiitake, heating rate and pH of Shiitake during the cooking had a direct effect upon the accumulation of 5'-nucleotides, being highest at 4ﾟC/min and pH 6.5, where phosphatase became more thermolabile than nuclease.
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