CONDENSED TANNINS IN CANOLA HULLS

The total content and the biological activity of tannins in canola hulls were determined in several samples of hulls of Westar, Cyclone, Excel, and Delta canola varieties. The contents of condensed tannins in canola hulls ranged from 14 to 1556 mg of catechin equivalents/100 g of hulls as determined by vanillin assay, up to 8 times more condensed tannins than reported previously. Both cultivar differences and the environmental growing conditions may have significant effects on the contents of condensed tannins in canola hulls. Statistically significant linear correlations (P less than or equal to 0.001) were found between the tannin content determined by the vanillin and the 4-(dimethylamino)cinnamaldehyde and the proanthocyanidin assays. Canola tannins had significant biological activity, as determined by the blue BSA assay. The results obtained using the proanthocyanidin and biological assays differed to a lesser extent than those obtained by the vanillin test. This suggests that condensed tannins isolated from low- and high-tannin hulls may differ in molecular weight.