Production of Flavonoid Pigments by Polyphenol Oxidase

Abstract

Flavonoid pigments were prepared from peanut skin or cocoa shell by treatment with microbial polyphenol oxidase. The extracts from peanut skin or cocoa shell turned brown with the polyphenol oxidase from Alternaria tenuis strain A-2. Impurities in the brown pigment solutions thus obtained were removed by the addition of ethanol followed by centrifugation, and then the brown pigments were precipitated by adjusting the solutions to pH 12 with sodium hydroxide. The precipitated pigments were dissolved in a small quantity of water, and the pigment solutions were powdered by freeze-drying after adjusting them to pH 6.5 with hydrochloric acid. The yield of peanut pigment or cocoa pigment was 15 0 or 16.5%, respectively. The flavonoid pigments thus obtained were water soluble and the color of them changed to orange-yellow with decreasing pH. These flavonoid pigments were stable against heat and light. Metal ions other than ferrous ion did not affect their color. While the peanut pigment was stable against chemical reagents, the cocoa pigment faded slightly with ascorbic acid or isoascorbic acid. The flavonoid pigments were good dyestuffs in acidic solutions and had a great affinity for wheat gluten. These pigments were applicable to drops, cookies or soft adzuki-bean jelly.