Effect of dehulling on the composition of antinutritive compounds in various cultivars of rapeseed

Eight different rapeseed cultivars (Brassica napus L.) have been dehulled by hand. The contents of glucosinolates, sinapine, condensed tannins and inositol phosphates have been investigated in the resulting fractions of dehulled seeds and hulls as well as in the whole seeds by HPLC methods and a spectroscopical method for condensed tannins. After dehulling the content of glucosinolates as well as the content of sinapine and inositol phosphates increased significantly (P = 0.01) in the seeds of the different cultivars by 2.0 to 35.0%, 14.1 to 57.1% and 11.9 to 38.2%, respectively. The content of condensed tannins decreased by 26.0 to 81.2% after the dehulling process. In most of the cultivars the enrichment of antinutritive compounds corresponded to the share of hulls separated from the seeds. Only in the case of condensed tannins unproportional losses in the dehulled seeds were observed.