Distribution of Total, Water-Unextractable, and Water-Extractable Arabinoxylans in Wheat Flour Mill Streams

Arabinoxylans are a minor but important constituent in wheat that affects bread quality, foam stability, batter viscosity, and sugar snap cookie diameter. Therefore, it is important to determine the distribution of arabinoxylans in flour mill streams to better formulate flour blends. Thirty-one genetically pure grain lots representing six wheat classifications common to the western U.S. were milled on a Miag Multomat pilot mill, and 10 flour mill streams were collected from each. A two-way ANOVA indicated that mill streams were a greater source of variation compared to grain lots for total arabinoxylans (TAX), water-unextractable arabinoxylans (WUAX), and water-extractable arabinoxylans (WEAX). TAX and WUAX were highly correlated with ash at r = 0.94 and r = 0.94, respectively; while the correlation for WEAX and ash decreased in magnitude at r = 0.60. However, the 5th middlings mill streams exhibited disparity between TAX and ash content as well as between WUAX and ash content. This may indicate that TAX and WUAX in mill streams are not always the result of bran contamination. Cumulative extraction curves for TAX, WUAX and WEAX revealed increasing gradients of arabinoxylans parallel to extraction rate. Therefore, arabinoxylans may be an indicator of flour refinement.