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Bran Size Distribution at Milling and Mechanical and Biochemical Characterization of Common Wheat Grain Outer Layers: A Relationship Assessment

¹UMR Ingénierie des Agropolymères et Technologies Emergentes, INRA, 2 Place Viala, 34060 Montpellier Cedex 01, France. ²ARVALIS, Institut du Végétal, 16 rue Nicolas Fortin, 75013 Paris, France. ³UMR Chimie Biologique, INA-PG, 78850 Thiverval-Grignon, France. ⁴Corresponding author. Phone: 33 (0)4 99 61 31 05. Fax: 33 (0)4 99 61 30 76. E-mail: lullien@ensam.inra.fr

Mechanical properties of wheat grain outer layers from common wheat (Triticum aestivum L.) cultivars known to display distinct milling behavior were analyzed using uniaxial tension tests. Tensile modulus and strain to rupture of the tissues distinguished between the wheat cultivars. Values of strain to rupture were related to coarse bran size generated by grain milling, a characteristic that distinguishes the two hardness classes. As content of an aleurone marker in total or first break flour was also related to coarse bran size, extensibility of wheat grain outer layers' could be a key parameter to explain the observed tissue mechanical behavior and thus distribution of the aleurone layer content in flours. As tissue mechanical properties are generally linked to the cell wall biochemical composition and structure, analysis of the main wheat outer layers' cell wall compounds was undertaken to establish relationships with the differences observed in mechanical properties. No clear correlation could be found with one of the wheat outer layers' component but involvement of the outer layers' cell wall structure in the tissues behavior at milling was confirmed.