VARIABILITY IN DEHYDRODIFERULIC ACID COMPOSITION OF DURUM-WHEAT (TRITICUM-DURUM DESF.) AND DISTRIBUTION IN MILLING FRACTIONS

The dehydrodiferulic acid content of different common and durum wheat grains and milling fractions was determined by an HPLC procedure. The 8-O-4', 5-8' benzofuran, 5-8' and 5-5' dehydrodimers were identified i n all samples studied and occurred in decreasing relative amounts, res pectively. Durum wheats were twice as concentrated in dimers as common wheats. An important genetic variation for dehydrodiferulic acid cont ent was shown within durum wheat grains, whereas the agronomic conditi ons had no effect. There was 10 to 20 times more dehydrodiferulic acid s in external layers (aleurone, bran) than in the starchy endosperm of durum wheat grains. The content and composition in dimers of the inne r endosperm did not vary according to genotypes and cultivation condit ions. The ratio of dehydrodimers to monomers of ferulic acid which rep resented an index of dimerisation, was 1.6 times higher in the externa l layers of the grain than in the endosperm. No relation was found, ho wever, between the degree of ferulic acid dimerisation and the milling behaviour of durum wheat grains. (C) 1998 Academic Press.