Protein-polyphenol interactions and in vivo digestibility of buckwheat groat proteins.

A rat model system, based on a diet with (Nb+) or without (Nb-) the inclusion of 0.7% of a 2:1 (w/w) mixture of Bacitracin and Neomycin sulfate (Nebacitin) was used to elucidate interactions of polyphenols with proteins in buckwheat. The treatment with the antibiotic Nebacitin suppresses the microflora in the large intestine and is used to obtain an estimate of the digestion occurring in the small intestine. Experimental buckwheat samples were obtained in order to contain different levels of polyphenol and were subjected to different hydrothermal treatments. It was found that a considerable interaction between polyphenols and proteins appeared during the hydrothermal treatment, and this interaction reduces the digestion of proteins through the small and large intestine. Microbial processes in the colon enhance the digestibility of protein, blocked by polyphenols in hydrothermally processed buckwheat.