Nagasaki University, Japan.
Int J Mol Sci. 2009 Dec 28;11(1):14-40. doi: 10.3390/ijms11010014.
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.
本文综述了食品加工过程中次生多酚化学的最新进展。介绍了红茶、威士忌、肉桂和柿子果实中次生多酚的产生机制。在红茶生产过程中，茶叶儿茶素被酶促氧化生成复杂的氧化产物混合物，包括茶黄素和茶红素。尽管这种饮料很重要，但由于混合物的复杂性，大多数化学物质尚未得到确认。然而，儿茶素氧化初始阶段的反应机制可以用简单的醌-酚偶联反应来解释。体外模型实验表明存在有趣的区域和立体选择性反应。将介绍最近关于反应机制的结果。在橡木桶中陈酿威士忌时，来自橡木的鞣花单宁被氧化并与乙醇反应，生成特征性的次生鞣花单宁。肉桂原花青素的主要部分通过与肉桂醛的共聚聚合。此外，通过氧化在聚合物分子中生成花色素苷结构单元，这解释了肉桂提取物的红色着色。该反应与乙醛缩合导致柿子果实中原花青素的不溶性有关。除了氧化，多酚与醛的反应在食品加工中可能很重要。
