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Influence of UV Exposure on Phenolic Acid Content, Mechanical Properties of Bran, and Milling Behavior of Durum Wheat (Triticum Durum Desf.)

¹INRA-ENSAM, Unité de Technologie des Céréales et des Agropolymères, 2, place Viala, 34060, Montpellier cedex 1, France. ²Corresponding author. Phone: (33) 4 99 61 22 02. Fax: (33) 4 67 52 20 94. E-mail: peyron@ensam.inra.fr.

Durum wheat bran was exposed to UV radiation up to 48 hr and the changes in ferulic acid (FA) content in the peripheral part s of grain were measured. The treatment resulted in a 25% decrease in FA monomer and a 44% decrease in dehydrodiferulic acid (DHD) ester-linked to the cell-wall arabinoxylans. This reduction was partly explained by a significant increase of FA (30%) and DHD (36%) engaged in hot alkali-labile linkages. The results suggest that UV irradiation induced the formation of new cross-links between feruloylated arabinoxylan and lignin in the pericarp. The effects of UV treatment on bran mechanical properties and wheat milling behavior were investigated. UV irradiation for 15 hr increased the stress to rupture by 30% and decreased the extensibility of bran tissues by 54%. This stiffening was associated with an increase in bran friability during grinding. Although this effect was due in part to the hydrothermal history of the grain, chemical modification induced by UV significantly influenced the size reduction of bran particles, which can be explained by the modification of the mechanical properties of bran. Relationships between the organization of cell-wall polymers, the mechanical properties of tissues, and the behavior of wheat grain during milling were investigated.