How gluten properties are affected by pentosans

During the wet separation of starch and gluten, both water extractable pentosans (WEP) and water unextractable solids (WUS) have a negative effect on gluten yield. Gluten properties are also affected: the gluten becomes less extensible. In comparison to the control, addition of WUS or WEP resulted in less gluten with a higher maximum resistance to extension (Rmax) and a smaller extensibility at maximum resistance (E at Rmax). The corresponding glutenin macropolymer (GMP) gel was more elastic, and the specific volume of the GMP particles was larger and their tendency to aggregate was lower. In contrast, the use of xylanase or ferulic acid (FA) resulted in a higher gluten yield and a larger E at Rmax of gluten. Here, the GMP was characterised by a more viscous gel structure, a smaller specific volume of the GMP particles and a larger tendency of GMP particles to aggregate. Correlations between gluten properties (Rmax, E at Rmax) and GMP particle properties ([η], K′) were observed. Based on these observations, we propose a possible explanation for the effect of pentosans on gluten formation and properties. Both a physical effect and a chemical effect are involved. The physical effect is related to viscosity and likely also to depletion attraction between protein particles. The chemical effect is related to a FA-mediated effect and 'controls' the tendency of the particles to aggregate (K′). The contribution of physical and chemical effects leads to a partial agglomeration of GMP particles and shifts the GMP particle size distribution to a higher value. Since GMP particle properties could be directly related to gluten rheological properties, this explains the change in quality observed. © 2004 Elsevier Ltd. All rights reserved.