Interaction of water unextractable solids with gluten protein: effect on dough properties and gluten quality

Abstract

In a previous study, we have shown that water unextractable solids (WUS) interfere with gluten formation and affect the quality of the resulting gluten. In this study we aim to explain how WUS can affect the process of gluten formation. To this end, WUS were modified with NaOH, xylanase, horseradish peroxidase (HRP) and hydrogen peroxide (H2O2). Effects of modified WUS on gluten yield, dough properties, and gluten and glutenin macropolymer (GMP) composition and properties were studied. The results showed that addition of WUS to wheat flour led to a lower gluten yield and gluten starch yield, a higher Rmax and a lower E at Rmax of gluten and a more concentrated and elastic GMP gel. Pretreatment of WUS by NaOH, xylanase, HRP and H2O2 cannot correct its negative effect on gluten yield, but addition of xylanase or free ferulic acid (FA) during gluten separation can remove or prevent the negative effect of WUS on gluten yield. Compared to addition of only WUS, addition of WUS and FA together to wheat flour resulted in a higher gluten yield, a higher E at Rmax of gluten, and a less concentrated and elastic GMP gel. Similar to water extractable pentosans (WEP), FA bound WUS plays a key role in the effect of WUS on gluten yield and properties. It appears that there is a common mechanism regarding the effect of WUS and WEP that the oxidative cross-linking during gluten formation could be prevented by FA addition. The difference between both is that WUS have a higher water binding capacity, which is reflected in a higher Rmax of dough and gluten in the presence of WUS.