ABSTRACT

A water-soluble tetrazolium salt XTT (3`-{l-[(phenylamino)-carbonyl]-3,4- tetrazolium}- bis(4-methoxy-6-nitro) benzenesulfonic acid hydrate) shows a unique reducibility for intermediates of the Maillard reaction, which is a typical reaction between amino groups and reducing sugars during heating process of foods. The practical milk samples showed the XTT reducibility. The severity of each treatment of milk samples significantly related with the extent of the reducibility. Interestingly, the reducibility was also shown to be effective for estimating the storage conditions such as the period and temperature. In the Maillard reaction in which lactose is involved, aminoreductone selectively reduces XTT, suggesting that the reducibility may be useful as a heating marker of dairy products. Additionally, the XTT reducibility reflected the heating severity of all model systems in which reducing monosaccharides or disaccharides were involved, suggesting that the XTT assay was applicable to the estimate the extent of heat treatment of not only milk but also other foods. In this review, we summarize analytical methods for determination of the Maillard reaction products of food and emphasize on the characteristic property of the XTT assay method.