Multi-scale organization and rheology of casein and pea protein mixed hydrogels formed by acidification: Effects of ratio and temperature.

The growing demand for sustainable food alternatives is driving increased research into mixed protein systems. In view of this scenario, this study aims to investigate the structural organization and rheological properties of mixed hydrogels formed by casein micelles (CMs) and pea protein through acid gelation, as well as to understand the effects of protein ratio and temperature on gel structure. The objective is to elucidate how these variables influence network formation at multiple scales, providing insights into the design of novel food structures. Small-angle X-ray scattering (SAXS), nuclear magnetic resonance (NMR), and rheological analyses were used to assess gel properties. The results indicate that mixed gels exhibit non-monotonic rheological behavior, with strong structural changes depending on the CM:pea ratio. At smaller scales (submicron sizes), there is no significant difference between pea or casein aggregates formed in mixed gels compared to those in pure gels. However, at larger scales (micron to tens of microns), the presence of pea in casein gels (or vice versa) has a significant impact on the protein network structure and gel properties, as seen in pore sizes and rheological behavior. Furthermore, temperature plays a crucial role, with effects observed at temperatures above 40 °C, mainly in casein-rich systems. This study provides a new perspective on the structuring of mixed protein gels and contributes to the development of hybrid food products.