Green Pigment Formed by the Reaction of Chlorogenic Acid (or Caffeic Acid Esters) with a Primary Amino Compound during Food Processing

Abstract

A marked greening observed in some foods, including sweet potato and burdock, during food processing was shown to be due to green pigment formation by the condensation reaction of two molecules of chlorogenic acid or caffeic acid ester with one molecule of a primary amino compound in air and alkali. The reduced and acetylated product of the green pigment was identified as a novel triphenol benzacridine derivative, and the yellowish ethanol solution of this product immediately turned green upon addition of butylamine or diluted alkali. Therefore, the green pigment was assumed to be a oxidized quinone type product of triphenol benzacridine. The structure was supported by comparison of the measured absorption spectra with those calculated theoretically. ESR studies indicated the presence of different types of free radical products in the green reaction mixture; one was determined to be a free radical product of the caffeate, and the others were assumed to be those of further oxidized green products. The formation mechanism of the benzacridine and oxidation products are proposed.A marked greening is observed in some vegetables, such as sweet potato, burdock and others, during some types of food processing and cooking, e.g., steamed bread containing small cubes of sweet potato which turned bluish-green after 3 Current address: Meitouku Yashirodai 2-175, Nagoya 465-0092, Japan.

Polyphenol oxidase/caffeic acid may reduce the allergenic properties of peanut allergens

“…In the absence of PPO, phenolic compounds are also known to be able to react with proteins. Such reaction is likely to take place under alkaline conditions7, 8 and during processing of foods 9, 23. Under alkaline conditions, a phenolic compound such as caffeic acid is easily oxidized to a quinone derivative, and, therefore, leads to cross‐linking of proteins (see Fig 1c).…”