Larger particle size of oat bran inhibits degradation and lowers extractability of β-glucan in sourdough bread – Potential implications for cholesterol-lowering properties in vivo

Abstract

Increased digesta viscosity is considered the mechanism underlying the cholesterol-lowering effect of oat β-glucan. Viscosity is mainly related to the molecular weight and concentration of solubilized β-glucan in the digesta and these should therefore be maintained at sufficiently high levels. Bread that includes oat bran is a potential source of β-glucan, but the baking process leads to degradation by β-glucanases present in the flours.In the current study, we investigated the effect of fermentation time as well as of particle size and content of oat bran in breads on the molecular weight, solubility and extract viscosity of β-glucan. Furthermore, we estimated the potential of the breads to have a cholesterol-lowering effect by comparison of molecular weight, solubility and extract viscosity of β-glucan with those of products known to have an effect in vivo.Longer fermentation time and smaller particles were found to lead to lower molecular weight of β-glucan. However, smaller particles also increased its extractability, leading to an overall increase in extract viscosities compared with coarse particles. Bread with the inclusion of 30% finely-milled, but not coarse oat bran was found to induce extract viscosity with the potential of producing a cholesterol-lowering effect despite more degraded β-glucan.