Enrichment of yoghurt with oat protein fractions: Structure formation, textural properties and sensory evaluation

Despite its excellent nutritional properties, unlike other cereals oat displays poor baking properties and therefore is mainly processed in products like rolled oats or serves as raw material for the functional ingredient β-glucan. During β-glucan production, a protein-rich fraction remains as a by-product. Functionalisation of this protein-rich oat-fraction and its application as a valuable food ingredient would improve the sustainability of the process. In the present study, oat protein-enriched cow's milk yoghurt was produced. The main foci were on the characterisation of techno-functional properties, as well as on the analysis of the organoleptic perception and sensory properties by a trained panel. Cow's milk yoghurt, following a traditional formulation with addition of skim milk powder (SMP), served as a reference. Oat protein was incorporated using two preparations: oat protein concentrate (OPC) and oat protein isolate (OPI). Fermentation of yoghurt enriched with SMP, OPC or OPI was monitored via pH-value, formation of lactic acid and rheological measurements. In addition, texture analysis and measurement of syneresis were performed and sensory properties were evaluated. Yoghurt containing SMP showed the highest strength in texture analysis but also a high rate of syneresis. Addition of OPC resulted in a product, which combines nutritional benefits with the sustainable use of the by-product of oat processing as well as improved product quality with respect to syneresis and sensory evaluation, especially mouthfeel. In case of OPI, strong sedimentation took place and high syneresis was observed. It is assumed that the compatibility of oat protein with milk proteins is low, which may be compensated by gelatinisation of starch during yoghurt production.