104 Effect of ferulic acid and laccase on wheat flour dough during mixing.

E. Labat, X. Rouau, P. FEILLET, and M.-H. Morel. Unité de Technologie des Céréales et des Agropolymères, INRA, 2 Place Viala, 34060 Montpellier Cedex 01, France.

The effects of ferulic acid (FA), an activated double bond compound, and laccase, a phenol oxidase, were studied during the mixing process of a wheat flour dough. The addition of FA provoked a rapid breakdown beyond the mixing peak. This effect was more important when both FA and laccase (yielding phenoxyl radicals) were added. Flour feruloylated arabinoxylans (AX) were solubilised partly during mixing. Laccase provoked their insolubilisation by chain-cross-linking through oxidative dimerization of AX-FA esters. Surprisingly the addition of exogenous FA increased the AX solubilisation during the process. The quantification of polymeric proteins, monitored by SE-HPLC, showed that FA and even more FA plus laccase increased the rate of proteins depolymerization during mixing. At the same time, the FA extraction yield went decreasing during mixing. An addition of phenoxyl radical on thyils radical, generated through the mechanical breakdown of inter-chains disulfide bonds might explain these results. It is likely that free FA reacted more easily with thyil radicals than FA esterified on AX chains due to a higher molecular mobility. However both FA and feruloylated AX should play a key role in dough breakdown, by blocking the thiol-disulfide interchange reaction.