Quantitative and Qualitative Study of Arabinogalactan-Peptide During Bread Making

Abstract

The quantitative and qualitative changes of water-extractable arabinogalactan-peptide (WE-AGP) and water-extractable arabinoxylan (WE-AX) in the flour from the two wheat varieties Skirlou and Soissons were investigated during a straight dough wheat bread-making process. The extractability of WE-AGP remained constant or increased slightly as a result of the bread-making process (increase: 12% for Skirlou and 10% for Soissons, expressed relative to the amount of WE-AGP initially present). This slight increase contrasts with the great increase in extractability of the WE-AX (29% for Skirlou and 77% for Soissons). No changes in arabinose-to-xylose ratio of WE-AX (0.47–0.50 (w:w) for Skirlou, 0.52–0.54 for Soissons) and arabinose-to-galactose ratio of WE-AGP (0.66–0.70 (w:w) for Skirlou, 0.69–0.72 for Soissons) occurred during the bread-making process. In contrast to differences found in the molecular weight distribution of WE-AX, no differences in the molecular weight distribution of WE-AGP were observed as a result of processing. Apparent molecular weights of 24,000 and 22,000 were found for WE-AGP samples of flour and doughs at different stages of the bread-making process for Skirlou and Soissons, respectively. The ¹H-NMR spectra (300 MHz, D₂O, 85°C) of the WE-AGP isolated from flour, dough and bread fractions were comparable. Taken together, the above data suggest that, unlike what can be observed in gluten agglomeration in dilute systems (Roels et al 1998), no specific interaction between WE-AGP and gluten proteins occurs in a straight dough bread-making process (Loosveld et al 1998).