Rheological properties and microstructure of soy-whey protein

Abstract Structured protein mixtures of plant and animal origin offer a pathway for the design of high protein food products with less ecological and economical footprint. This approach can also be used to adapt a nutritional requirement for specific consumers. The rheological properties, distribution and interaction of proteins, and structural characteristics of mixtures of soy protein isolate (SPI) and whey protein isolate (WPI) at different ratios with a total protein concentration of 6, 12 or 16% (w/v) were studied using small deformation rheology, sodium dodecyl sulfate-poly- acrylamide gel electrophoresis and confocal laser scanning microscopy. Upon heating to 95 °C, whey protein formed the primary structure of protein network in all of the SPI/WPI mixed systems. Reduction of WPI in the mixed protein systems led to weakening of the gel strength. SPI acted primarily as particulate fillers but the hydrophobic associations between SPI and WPI additionally contribute to the overall elastic property. The gel network structure itself, thus, was found to depend on the amount of SPI in the mixed protein system. Hence, altering the ratio of SPI and WPI could produce protein gels at the similar strength but with different microstructures and at various protein concentrations.