Determination of Both Tannin and Protein in a Tannin-Protein Complex

A method for determination of both protein precipitation capacity of tannins and protein-precipitable phenolics and the ratio of protein to tannin in a tannin-protein complex is presented. The relationships of both bovine serum albumin (BSA) precipitated and the protein-precipitable phenolics with tannic acid and the ratio of BSA and tannins in the protein-tannic acid complex agreed well with those obtained from the methods already available. The above parameters were also determined for Quercus incana leaves at different stages of maturation. The protein precipitation capacity and protein-precipitable tannins decreased substantially with maturation, whereas the ratio decreased slightly. As the present method allows determination of these parameters from a tannin-protein complex, it is convenient, takes less time, can handle a large number of samples at a time, and requires less tannin-containing extracts and chemicals compared to other available methods.