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Research Project: Enhance Wheat Quality, Functionality and Marketability in the Western U.S.

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Title: Arabinoxylan content and characterisation throughout the bread-baking process

Author
item Kiszonas, Alecia - Washington State University
item Fuerst, E - Washington State University
item Luthria, Devanand - Dave
item Morris, Craig

Submitted to: International Journal of Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2015
Publication Date: 7/22/2015
Publication URL: http://handle.nal.usda.gov/10113/61150
Citation: Kiszonas, A.M., Fuerst, E.P., Luthria, D.L., Morris, C.F. 2015. Arabinoxylan content and characterisation throughout the bread-baking process. International Journal of Food Science and Technology. 50:1911-1921.

Interpretive Summary: Wheat end-use quality is heavily influenced by the non-starch polysaccharide molecules, arabinoxylans (AX). The high water-absorption capability of AX molecules creates differing water relationships in various types of wheat-based products. While the influence of AX content has been heavily studied in both hard and soft wheat products, the structure of these AX molecules has not received the same level of examination. The objective of this study was to evaluate the content and structure of AX molecules throughout the bread-baking process in order to further understand the intermolecular relationships that AX molecules participate in. Arabinoxylan molecules can be quantified into three categories: total AX content (TAX), water-extractable (WEAX) content, and water-unextractable (WUAX) content. The content and structure of these three categories was assessed in flour, mixed dough, proofed dough, bread crumb, bread upper crust, and bread lower crust for both refined and wholemeal flour samples from five different varieties representing different market classes of wheat. The TAX, WEAX, and WUAX content and structure were observed to differ between refined flour and wholemeal samples. Both types of flour exhibited similar patterns, however, of the way AX molecules influenced loaf volume. Most beneficial to enhanced loaf volume development were WEAX molecules with low levels of arabinose substitution, likely protecting and strengthening the protein foam and gluten network. The WUAX molecules apperaed to inhibit full gluten development. It was determined that although AX content does play a substantial role in bread quality, the structural characteristics and differences of the AX molecules were more influential in bread quality differences.

Technical Abstract: End-use quality of wheat (Triticum aestivum L.) is influenced in a variety of ways by non-starch polysaccharides, especially arabinoxylans (AX). The assessment of AX content and structural properties is often performed on flour and extrapolated to predict the role that AX may play in baked products. Few studies have focused on changes in AX content and properties during processing and baking. The objective of this study was to track total and water extractable AX (TAX and WEAX) throughout the bread baking process of three hard and two soft wheat varieties, using both wholemeal flour and refined flour. The TAX and WEAX content, as well as the ratio of arabinose:xylose was assessed in flour, mixed dough, proofed dough, and the bread loaf, separated into crumb, upper crust, and bottom crust. As expected, refined flour of hard wheat varieties exhibited the highest bread quality, as assessed by loaf volume. The content changes of TAX during the baking process differed between the refined flour and wholemeal samples, suggesting a change in the TAX availability which we ascribe to molecular interactions and heat treatment. WEAX content dramatically decreased during baking, suggesting that oxidative cross-linkages rendered it unextractable. Higher levels of WEAX and lower levels of arabinose substitution were correlated with higher loaf volumes for refined flour in the hard wheat varieties. Having a better understanding of the importance of both WEAX content and arabinose substitution allows for directed breeding efforts toward improved hard wheat varieties for optimum bread-baking.