The influence of cooking on the antioxidant properties and polyphenol content in buckwheat, barley and millet groats and the transfer of the compounds to the water

The research subject was the influence of the cooking process on the polyphenol content and antioxidant properties of groats (buckwheat groats, barley groats, millet groats) and on the colour parameters of the products. After groats cooking, also the water was tested for the polyphenol content and antioxidant properties that permeated into the decoction of the cooked raw material. The evaluation of the antioxidant properties of groats was conducted with the DPPH radical assay, the polyphenol content was determined with the Folin-Ciocalteu reagent, and the colour was determined with the trichromatic colorimetry method using the Konica Minolta CM-5 colorimeter (Osaka, Japan). The cooking process significantly lowered the content of polyphenolic compounds and antioxidant properties of the ready products. The best antioxidant properties after cooking were found in buckwheat groats and the weakest in millet groats. The polyphenol content in cooked products depended on the type of groats. Cooking significantly decreased the polyphenol content, but only in buckwheat and barley groats, as well as causing a change of groats colour as compared to uncooked samples. The most antioxidant properties were found in the water from cooking barley groats, and the least - from cooking millet groats. The most polyphenols permeated into the water from cooking buckwheat groats, and the least from cooking millet groats. All groats, except millet groats, darkened after cooking. In all types of groats, the correlation coefficients between colour parameter and general polyphenol content and the ability to scavenge DPPH radicals showed very strong negative dependences. The conducted research can help in designing the technological process of cooking buckwheat, barley and millet groats, and a way of using the water from cooked groats for consumption.