Peer review

The nucleosidases and nucleoside deaminases of barley and malt were studied with respect to their development during germination and to the effect of gibberellic acid and kiln and mashing heat on their activities. The activities of the nucleosidases that attack adenosine, inosine, cytidine, and uridine and the deaminases that attack adenine, adenosine, cytosine, and cytidine are relatively low in barley. The four nucleosidases and cytidine deaminase develop appreciable activity during germination. The application of gibberellic acid had a statistically significant effect only on adenosine and uridine nucleosidase. All of the enzymes appeared to be largely unaffected by a kilning temperature of 85°C. In mashing, adenosine and inosine nucleosidases and adenine and cytidine deaminases declined as the temperature rose to 70°C, and no activity was observed after 60 min at 70°C. Uridine and cytidine nucleosidase activities are very low, but fairly stable, during mashing. Commercial brewers' malts show high levels of adenosine, inosine, and uridine nucleosidases and cytidine deaminase.

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