PURIFICATION OF COMMERCIAL GRAPE PIGMENT

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Abstract
Although red grape pigments have been studied and shown to be small molecular weight substances called anthocyanins, it was found that commercial grape pigment extracts are highly polymerized and contaminated with microbial nutrients. Thus, when the pigments are used to color drinks in the absence of preservatives, spoilage is enhanced. The pigments are highly dispersed in molecular weights, tentered about 12,000 daltons by ultracentrifugation methods. Ultrafiltration membranes with molecular weight cut‐off of 10,000 and ion exchange have been used successfully to remove contaminants, particularly when employed in conjunction with a cation exchange treatment. When purified pigments are used to color drinks, there is a minimum proliferation of yeasts. Factors affecting purification efficiency, pigment stability, and yeast population kinetics are discussed. Purified pigment has a higher tinctoral power, enhanced stability and, when dried, is not hygroscopic. It has characteristics of anthocyanin and tannins. It is, therefore, called Anthocyanotannin.