Protein precipitating capacity of condensed tannins of beach pea, canola hulls, evening primrose and faba bean

Condensed tannins (CT) from beach pea. Cyclone canola hulls, evening primro se and faba bean were extracted into 70% (v:v) aqueous acetone. The lyophil ized extracts were then purified on a Sephadex LH-20 column using first 95% ethanol as a mobile phase for elution of non-tannin phenolics and then 50% aqueous acetone to elute CT. Condensed tannins isolated from beach pea pos sessed shorter polymer chains than those isolated from canola hulls, evenin g primrose or faba bean. Bovine serum albumin (BSA) was effectively precipi tated by beach pea CT at pH values between 3.5 and 5.0. CT of canola hulls, evening primrose and faba bean precipitated BSA at pH 4.0-5.0. A statistic ally significant (P=0.0001) linear relationship existed between the amount of tannin-protein complex formed and the amount of CT added to the reaction mixture. The slopes of these lines indicated that evening primrose CT were the most effective protein precipitants, followed by canola hulls, faba be an and beach pea CT. Based on the amount of gelatin and BSA required to inh ibit 50% of dye-labelled BSA-CT complex precipitation, gelatin was 10 times more effective as a precipitation inhibitor than unlabelled BSA. (C) 2001 Elsevier Science Ltd. All rights reserved.