Distribution of Carbohydrates in Gluten Fractions Isolated from European Wheats (Triticum aestivum L.) in a Batter System

Abstract

Glucose represented 89% of the total carbohydrate of gluten isolated in a batter system from wheat cultivars exhibiting varying breadmaking qualities. Galactose, arabinose (Ara), and xylose (Xyl) were the remaining carbohydrates (ca. 10% of the total carbohydrate content), while mannose was present in minor quantities (<1%). After Pronase treatment ca. 43% of the Ara and ca. 52% of the Xyl originating from arabinoxylan (AX) could be solubilized, indicating the presence of water extractable as well as water unextractable AX. Arabinogalactan-peptide (AGP) and small amounts of β-glucan were also present. Water extractable AX with a low Ara-to-Xyl ratio (A/X) and thus a low degree of substitution preferentially are incorporated in the gluten network probably as a result of alignment between glutenin polymers and AX in the stirring direction. In gluten from cultivars exhibiting high gluten protein recoveries (see accompanying paper; Roels et al. J. Agric. Food Chem. 1998, 46, 1344−1349), the levels of total gluten associated nonstarch polysaccharides (TOTGANSP), expressed as a percentage of total flour NSP, were also high. It was postulated that the gluten proteins of such cultivars agglomerate despite the presence of NSP since the gluten fractions with the best agglomeration properties contained the lowest amount of NSP. In the aforementioned gluten fractions the AGP/AX ratio was also unusually high, indicating that the undocumented role of AGP in wheat gluten agglomeration may well be underestimated. Keywords: Gluten agglomeration; gluten composition; arabinoxylan; arabinogalactan; Triticum aestivum