Effect of processing on the solubility and molecular size of oat ß-glucan and consequences for starch digestibility of oat-fortified noodles.

ABSTRACT

White wheat salted noodles containing oats have a slower digestion rate those without oats, with potential health benefits. Oat ß-glucan may play an important role in this. Effects of sheeting and shearing during noodle-making and subsequent cooking on ß-glucan concentration, solubility, molecular size and starch digestibility were investigated. The levels of ß-glucan were reduced by 16% after cooking, due to the loss of ß-glucan into the cooking water. Both the noodle-making process and cooking increased the solubility of ß-glucan but did not change its average molecular size. Digestion profiles show that ß-glucan in wholemeal oat flour did not change starch digestion rates compared with isolated starch, but reduced the starch digestion rate of oat-fortified wheat noodles compared to the control (wheat noodles). Confocal laser scanning microscopy suggests that interaction between ß-glucan and protein contributes to the starch-protein matrix and changes noodle microstructure, and thus alters their digestibility.