Evaluation and Optimization of Emulsifying Properties of Mixed-Plant Proteins in Oat-Based Cooking Cream

Sammanfattning

The development of plant-based foods has increased interest in sustainable and natural protein-based emulsifiers that may partially replace conventional/synthetic emulsifying ingredients. Rapeseed press cake is an underutilized protein rich side stream from oil production with potential for valorization as a functional food ingredient. This study evaluated the emulsifying properties of protein fractions recovered from cold-pressed rapeseed press cake (RPC), their combination with wheat bran protein concentrate (WBPC), and their application in an oat-based cooking cream formulation. Rapeseed proteins were obtained by alkaline extraction followed by acid precipitation, yielding supernatant and precipitate fractions. Their emulsifying properties were evaluated in oil-in-water emulsions by measuring droplet size under different protein-to-oil ratios, homogenization pressures, and homogenization cycles. The precipitate fraction had a higher protein content and protein recovery than the supernatant fraction, with protein content of 55.43 ± 1.53% and 19.56 ± 0.24%, respectively. Despite this, the supernatant fraction showed greater emulsifying efficiency. Its optimal conditions in the buffer-based model system were identified as a protein-to-oil ratio of 0.4% (w/w), a homogenization pressure of 300 bar, and one homogenization cycle, while the precipitate fraction required approximately 11% (w/w) at 250 bar. A second homogenization cycle did not improve emulsion formation for either of the fractions. Blending rapeseed supernatant protein with WBPC did not produce a synergistic improvement in emulsifying performance, as the formulation containing 100% rapeseed supernatant protein formed the smallest droplets among the tested protein blends. In the oat based cooking cream system, the original control formulation containing Panodan with Xanthan Gum produced the smallest droplets (d32=0.51 μm; d43=1.65 μm). Nevertheless, among the protein-based alternatives, replacing Panodan with rapeseed supernatant protein while retaining Xanthan Gum gave the best performance (d32=1.15 μm; d43=7.03 μm). These findings indicate that rapeseed supernatant protein has potential as a natural partial replacement for conventional emulsifiers in plant-based food formulations, thereby increasing the potential value of rapeseed press cake as a source of functional protein ingredients.