Contents and Structural Features of Water-Extractable Arabinogalactan in Wheat Flour Fractions

Abstract

In Camp Remy Bühler MLU-202 roller mill flour fractions, the levels of water-extractable arabinoxylan (WE-AX) (0.30−0.41%, dry basis) were comparable to those of water-extractable arabinogalactan (WE-AG) (0.29−0.38%, dry basis). Minaret had more WE-AX (0.49−0.68%, dry basis) than WE-AG (0.27−0.36%, dry basis). The ratio of WE-AG to WE-AX for the different flour fractions varied between 0.83 and 1.03 for Camp Remy and between 0.46 and 0.57 for Minaret. For both wheat varieties, the percentage of WE-AX and WE-AG was higher for the second and third reduction roll fractions than for the three break and the first reduction roll fractions. There was little structural variation in WE-AG of different flour fractions. The arabinose to galactose (A/G) ratio (w/w) varied between 0.63 and 0.69 for Camp Remy WE-AG and between 0.66 and 0.72 for Minaret WE-AG. The molecular weight range of the water-extractable arabinogalactan-peptide (WE-AGP) isolated from the different flour fractions of Camp Remy and Minaret was 5 × 10 4 −10 × 10 4 . The 1 H NMR spectra of the WE-AGP isolated from the different flour fractions were comparable and display the following diagnostic peaks (300 MHz, D 2 O, 85 °C): δ 5.26, anomeric protons of α-linked arabinofuranosyl residues; and δ 4.47−4.54, anomeric protons of β-linked galactose residues. Keywords: Arabinogalactan; arabinoxylan; wheat flour; milling