Towards creating sustainable foods from side streams: Heat-induced structure formation in blends of sunflower seed press cakes and cheese whey under moderate shear

Abstract

Processing of oilseeds generates low value by-products, which still contain valuable components. Sustainable and circular food chains require valorising the entire stream or producing less refined fractions of it. One approach could be blending with other protein-containing side streams to obtain novel, nutritionally valuable and techno-functional food ingredients. In this study, sunflower press cake was co-processed with components from whey, a cheese-making by-product. Blends with constant dry matter and protein content but different press cake to whey protein ratios (0–225 g/kg press cake) were used to investigate the contributions of both side streams to structure formation during heating (80–140 °C) under moderate shear using a Rapid Visco Analyser. The denaturation of whey proteins contributed to an increased viscosity, but the highest viscosities were still achieved at high ratios of press cake, underlining the importance of the fibre fraction for structure formation. Treatments at 120 and 140 °C increased the amount of insoluble material and water holding capacity of the blends, and analyses of the serum phase and curd showed that sunflower and whey proteins formed heat-induced, insoluble aggregates. Confocal laser scanning microscopy confirmed the presence of large protein particles dispersed in the matrix rather than the presence of a continuous network, as was the case for heating without shear. Furthermore, the protein particles were more defined and showed a smoother appearance with increasing press cake concentration. This research provides fundamental insights in the colloidal interactions between biomacromolecule blends during processing (e.g., protein cross-linking, microphase separation), and demonstrates the importance of understanding the critical process parameters (e.g., heat, shear) leading to structure formation, facilitating the successful integration of complex materials such as press cakes and setting the basis for further processing of the blends and their utilisation as ingredients, for instance in functional drinks, snacks, or semi-solid spreads.