[In vitro interaction of polyphenols of coffee pulp and some proteins]

The in vitro interaction of pure polyphenols and polyphenol extracts of coffee pulp with pure proteins was studied. The polyphenols used for the assays were tannic acid, chlorogenic acid and catechin, and the proteins were gelatin, casein and bovine serum albumin (BSA). Different pHs and different polyphenol/protein ratios were used in the experiments. Extracts of coffee pulp in methanol, methanol-water (50:50), ammonium hydroxide 3%, and calcium hydroxide 1%, were used. In general, the maximum binding of polyphenol with protein was obtained at a polyphenol/protein ratio of 1/2, at a pH of 5.0. The higher binding percentages were found with the ammonium hydroxide extract and with tannic acid. The lowest binding percentage was obtained with the methanol-water extract. The other extracts presented intermediate binding degrees. The results herein reported demonstrate that the polyphenols of coffee pulp have capacity to bind proteins in vitro at the pHs assayed. This phenomenon may be the cause of the deficient protein utilization when coffee pulp is included in the animals' diet.