Wheat grain arabinoxylan quantification, characterization, and fate during baking.

摘要

The study of wheat (Triticum aestivum L.) as it relates to end-use quality is highly diverse. This dissertation examines end-use quality across the U.S. and how the non-starch polysaccharide arabinoxylan (AX) influences wheat quality. Arabinoxylans occur in water-extractable (WEAX) and water-unextractable fractions. First and foremost, an accurate, precise, and consistent method of quantifying AX was critical to ascertain. Gas chromatography-flame ionization detection was preferred over a colorimetric phloroglucinol assay for consistency and accuracy. A survey of soft and hard wheat grown in distinct nurseries across the U.S. was undertaken to further understand genetic and environmental influences on wheat quality across the U.S. High levels of variation were observed across and within each growing region. Specific grain, milling, and baking quality traits were determined to have potential predictive power in determining overall end-use quality. The soft wheat varieties with very high and very poor quality were assayed for AX content. In two of the four nurseries studied, AX negatively influenced cookie diameter. The total AX content was heavily influenced by genetics, whereas WEAX content was more variably influenced by genetics and environment. Two studies were undertaken to further understand the role total AX and WEAX play throughout the baking process of pancakes and bread. In wholemeal pancakes, total AX exhibited a strong negative influence on pancake quality, whereas in refined flour pancakes, WEAX was the greatest contributor to decreases in pancake quality. The AX molecules differed in their availability for quantification throughout the baking process, suggesting that those molecules unavailable for quantification were involved in intermolecular interactions. In bread, total AX availability differed throughout the baking process, suggesting complex intermolecular interactions. The molecular substitution of the AX molecules influenced the intermolecular relationships occurring throughout the baking process, and eventually impacting final quality of the bread loaf. In particular, the substitution pattern of WEAX was the most critical factor in determining the extent to which WEAX molecules enhanced loaf volume. These studies clearly indicate that there are more complex molecular interactions occurring than have previously been elucidated, necessitating further studies on how AX molecules influence final end-use quality.