Polyphenols as Colorants.
The market for natural colors for food applications is ever increasing. Consumers are seeking simpler and cleaner labels for their foods and are looking for alternatives to synthetic ingredients. As a result, interest in natural products including natural colorants is obvious. This review explores the potential of polyphenols and polyphenol derived molecules as colorants. Anthocyanins are well known colored flavonoids but other polyphenols including many aurones and chalcones derivatives are also colored.
Anthraquinone based pigments occur in nature, one of which is tetrahydroxylated anthraquinone – carminic acid. Carminic acid and its lake are commonly used pigments and provide a red to pink hue depending on pH of a food or beverage. Usually colorless polyphenols can give rise to colored
products by virtue of presence of enzymes or reaction with other substrates or both. Polyphenol oxidase (PPO) plays an important role in these reactions.
Tea pigments are a good example where PPO oxidizes Epicatechin and epicatechin-3-O-gallate (EGCG) and other polyphenols. The reaction products being very unstable in nature interact chemically and generate pigments. During cocoa processing the nibs undergo fermentation, leading up to enzymatic reactions causing color development at the expense of polyphenols. Avocado seeds undergo similar reactions in presence of PPO and oxygen. Non-flavonoids include phenolic acid derivatives, stilbenes, tannins and lignins. These compounds are mostly colorless or light yellow/brown and rarely contribute to the color of foods. However natural colors, i.e. colorants derived from natural sources, fall under color additives exempt from certification’ per the regulations devised by United States (US) Food and Drug Administration (FDA).
Adv Food Technol Nutr Sci Open J. 2016; SE(2): S1-S6. doi: 10.17140/AFTNSOJ-SE-2-101