The Increase of Indophenol Reducing Value of Boiled Potato (3)

Abstract

The contribution of the system of DOPA, tyrosine and polyphenol oxidase to the remarkable increase of indophenol reducing value during the boiling procedure of the aqueous extract of potato was investigated and discussed. When the red solution of resulting DOPAchrome by the action of polyphenol oxidase on DOPA and tyrosine at the level of potato juice was heated, the solution turned from red to colorless and simultaneously the indophenol reducing value increased remarkably. And it seems that the resulting indophenol reducing substance is a sort of reductone, 5,6-dihydroxyindole. The system of other polyphenols gave little increase of indophenol reducing value. Therefore the system of DOPA, tryosine and polyphenol oxidase is specific to the above increase.