Potential of redcurrant protein-enriched fractions as emulsifier in oil–water-emulsions

Abstract

Berry protein, due to its functional properties, was extracted from redcurrant pomace seeds (RPS) in aqueous media to utilise side-streams and increase the sustainability of food production. Emulsions containing 1% redcurrant seed protein and 10% rapeseed oil were prepared by high pressure homogenisation. The emulsions’ structure, droplet surface charge, stability, rheological behaviour, and colour were characterised by microscopy, dynamic laser light scattering, storage tests and bulk rheology including large amplitude oscillatory shear rheology, respectively. Protein extracts of RPS proved to stabilise oil–water-interfaces by formation of a protein film having non-linear flow characteristics. While at low to medium shear, the emulsions showed pseudoplastic behaviour, limited molecular mobility at the interface induced softening at high shear. The shear stability of the interfacial protein layer decreased with increasing pH, i.e. with increasing molecular charge. Emulsions were prone to flocculation and subsequent creaming, either because of low surface charge at low pH or due to bridging by proteins and polymerised polyphenol complexes under neutral conditions. Although redcurrants only occupy a small market share in the berry sector, they are of high importance for specialised local producers and results presented here might evince possibilities for the utilisation of other pomace types.