The influence of polyphenols on generation of free radicals as the precursors of Maillard reaction products

Abstract

Thermally treated foods, like bakery products, contain Maillard reaction products some of which are proved as the substances with antioxidant properties. There are many literature data stating that Maillard reaction products together with polyphenols as the potent antioxidants contribute to the overall antioxidant capacity of some bakery products. It was found that pyrazine cation radicals are the precursors in formation of Maillard reaction products. The aim of this work was to investigate the interaction of these radicals with some polyphenols that are frequently contained in ingredients used for bakery production. The formation of relatively stable free radicals in alkaline reaction mixtures (pH 9.0) of the model systems consist of D(+)-glucose (1.0 M) and structural isomers of aminobutanoic acid (1.0 M) heated at the temperature of 98 °C for 20 minutes has been detected by electron spin resonance (ESR) spectrometry. Based on the analyses of hyperfine structure of ESR spectra of reaction mixtures of model systems, the presence of 1,4-disubstituted pyrazine cation radicals formed at the initial stage of Maillard reaction was found. Different polyphenols (gallic, caffeic, ferulic, chlorogenic acid, and tannic acid) were added in model systems to investigate their influence on the generation of pyrazine cation radicals. Decrease of relative intensities (RI) of ESR spectra signals indicated polyphenols' ability to inhibit the generation of the pyrazine cation radicals. It was found that tannic acid was the most efficient of all investigated polyphenols in inhibiting the formation of free radicals at the initial stage of Maillard reaction followed by gallic > caffeic ≥ chlorogenic > ferulic acid. These findings indicate a complex relation between antioxidants and the precursor of Maillard reaction products. Further investigation is needed to reveal the overall contribution of both polyphenol(s) and Maillard reaction products to antioxidant capacity of thermally treated product.