Towards hybrid protein foods: Heat- and acid-induced hybrid gels formed from micellar casein and pea protein

Given the rising demand for more sustainable, cookable dairy alternatives, this research explores the formation and characteristics of heat- and acid-induced gels combining micellar casein and pea protein. Protein dispersions (4 % w/w) of commercial micellar casein isolate and pea protein isolate were prepared and preheated (95°C, 30 min) separately before mixing in varying ratios (75:25 %, 50:50 %, and 25:75 % w/w). After emulsifying with milk fat (3.5 % w/w), the protein mixtures were heated to 80 °C and acidified to pH 5.2 (citric acid). The resultant coagula were pressed, drained, and molded to obtain the final gel. It was observed that adding pea protein led to a higher yield of coagula with more serum retained. As the proportion of pea protein increased, the total solids (TS), protein, and fat content of the gels decreased linearly. The micellar casein gel showed significantly higher hardness, elasticity, and chewiness than the gels containing pea protein. Moreover, the micellar casein gel did not show clear fracture behavior under large deformation, while the gels containing pea protein were more prone to rupture. These textural differences were explained by the changes in gel compositions, protein interactions, and gel microstructure. The composition and textural properties of hybrid gels showed a strong linear relationship with pea protein fractions, showing the possibility of customizing gel properties. Notably, the hybrid gel containing 25 % pea protein exhibited promising characteristics, closely resembling those of the commercial dairy paneer product.