Int. J. Mol. Sci. 2010, 11(1), 14-40; doi:10.3390/ijms11010014
Review

Chemistry of Secondary Polyphenols Produced during Processing of Tea and Selected Foods

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Received: 19 November 2009; in revised form: 19 December 2009 / Accepted: 24 December 2009 / Published: 28 December 2009
(This article belongs to the Special Issue Phenolics and Polyphenolics)
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract: This review will discuss recent progress in the chemistry of secondary polyphenols produced during food processing. The production mechanism of the secondary polyphenols in black tea, whisky, cinnamon, and persimmon fruits will be introduced. In the process of black tea production, tea leaf catechins are enzymatically oxidized to yield a complex mixture of oxidation products, including theaflavins and thearubigins. Despite the importance of the beverage, most of the chemical constituents have not yet been confirmed due to the complexity of the mixture. However, the reaction mechanisms at the initial stages of catechin oxidation are explained by simple quinone–phenol coupling reactions. In vitro model experiments indicated the presence of interesting regio- and stereoselective reactions. Recent results on the reaction mechanisms will be introduced. During the aging of whisky in oak wood barrels, ellagitannins originating from oak wood are oxidized and react with ethanol to give characteristic secondary ellagitannins. The major part of the cinnamon procyanidins is polymerized by copolymerization with cinnamaldehyde. In addition, anthocyanidin structural units are generated in the polymer molecules by oxidation which accounts for the reddish coloration of the cinnamon extract. This reaction is related to the insolubilization of proanthocyanidins in persimmon fruits by condensation with acetaldehyde. In addition to oxidation, the reaction of polyphenols with aldehydes may be important in food processing.
Keywords: polyphenol; oxidation; black tea; catechin; proanthocyanidin; ellagitannin
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MDPI and ACS Style

Tanaka, T.; Matsuo, Y.; Kouno, I. Chemistry of Secondary Polyphenols Produced during Processing of Tea and Selected Foods. Int. J. Mol. Sci. 2010, 11, 14-40.

AMA Style

Tanaka T, Matsuo Y, Kouno I. Chemistry of Secondary Polyphenols Produced during Processing of Tea and Selected Foods. International Journal of Molecular Sciences. 2010; 11(1):14-40.

Chicago/Turabian Style

Tanaka, Takashi; Matsuo, Yosuke; Kouno, Isao. 2010. "Chemistry of Secondary Polyphenols Produced during Processing of Tea and Selected Foods." Int. J. Mol. Sci. 11, no. 1: 14-40.

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