Evaluation of Neopurpuratin, a Purplish-red Substance Produced by Microorganism, as Food Colors

Abstract

Aqueous solution of neopurpuratin, obtained by mixed culture of Streptomyces propurpuratus with Bacillus sp. No. 751, shows a vivid purplish-red. Therefore, it's use for food colors was studied. By the physicochemical studies, it was revealed that the stability constant(log K) of neopurpuratin, chelate complex of Fe²⁺, was 14.19(pH5, 25°C)which was as high as that of EDTA and Fe²⁺. The color tone in aqueous solution on neopurpuratin was fairly stable in a wide range of pH(3.6-8.2)and was not affected by light but it's fading was observed by heating and also by the addition of chelating agents or metal ions such as Cu²⁺, Co²⁺, Fe³⁺, Zn²⁺ etc. It was possible to prevent fading significantly by the addition of reducing agents such as vitamin C. Application of neopurpuratin as food colors was studied on non-cooked foods and it was found to be available for coloring soft drinks, jellies, pickles and others. Neopurpuratin was suggested to be safe in the biological tests(acute toxicity and mutagenicity).