Polyphenols as Colorants

Abstract

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. Polyphenols are classified into flavonoids or non-flavonoids and are known for their antioxidant and biological activity. Anthocyanins are well known colored flavonoids but other polyphenols including many aurones and chalcones derivatives are also colored. Curcumin, demethoxyxurcumin, bisdemethoxycurcumin and cyclocurcumin are isolated from turmeric. Turmeric extract is used as a colorant in many food applications owing to its high heat stability. 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. Typically polyphenol content is lower after these reactions occur. 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. Similarly in wine, new pigments called pyranoanthocyanins are generated from anthocyanins. During juice extraction in apples, colored products are formed from colorless chalcones as a result of PPO activity. PPO products have been thought to be polymeric in nature but in the reviewed studies that is not the case. Among the polyphenols discussed in the study, aurones, chalcones and Hydroxy-anthraquinones (HAQs) have not been exploited to full potential. More research on optimizing isolation of pigments and using in food systems is needed. Regulatory hurdles will need to be cleared to enable their use in food applications.

Comparison of the Total Polyphenol Content and Antioxidant Activity of Chocolate Obtained from Roasted and Unroasted Cocoa Beans from Different Regions of the World

“…Polyphenols shape not only antioxidant properties, but also affect sensory properties such as colour and taste [14,16,17]. During all stages of processing, the polyphenols present in cocoa beans may undergo many transformations, including polymerization, hydrolysis or reactions with proteins [18].…”

Rhus coriaria (Sumac): A Magical Spice

“…Rhus coriaria use as colorant, as the sumac anthocyanins (main phenolic compound) are considered one of the pigmenting compounds in it with stability, are increased by intermolecular pigmentation after other polyphenolic addition interacting without covalent bond formation with the molecules preventing the nucleophilic attack by water molecule, making a more stable water mixed colorant agent extract [52].…”

The Use of Syrian Sumac (Rhus coriaria) as a Meat Tenderizer: Effect on Fat, Protein and Collagen Profiles on Pectoralis superficialis Cut

“…Rhus coriaria uses in the Food Industry: In addition, researchers have been analyzing its potential as preservatives (Abdelmalek, 2013;Obais, 2013), antioxidant (Bursal, 2010;Almouwaly, 2013) and colorant (Dabas, 2016) for its use in the food industry.…”