Upcycling of minimally processed oat okara: Dietary fibre enrichment of wheat bread

Abstract

With the increasing production of oat-based milk alternatives, a by-product with high nutritional value is generated in considerable amount. Due to its high moisture content, this so-called oat okara demands for subsequent processing strategies to ensure safe storage and further utilisation in food production. In this study, three okara from two manufacturers were dried and milled in lab-scale. The okara powders were then used as wheat flour substituents (5 and 10 g/100 g) in bread making. Despite differences in nutritional composition because of variations in the raw material or processing parameters during beverage production, protein (27–50 g/100 g) and insoluble dietary fibre (27–38 g/100 g) represented the main fractions in crude okara. When freeze drying was applied instead of convective drying, thermally induced changes (e.g. discolouration) were avoided. Solubility and moisture sorption increased for okara with higher contents of soluble dietary fibre and non-dietary fibre carbohydrates. With increasing okara substitution, breads showed reduced baking loss, a more compact structure and higher crumb firmness. Significant differences in taste (nutty, salty, grainy), odour (nutty, yeasty) and consistency (fibrousness) were observed in sensory assessments. The findings highlight the potential of dried okara as a valuable food ingredient for protein and fibre enrichment.