Acid-induced mixed methylcellulose and casein gels: Structures, physical properties and formation mechanism

In this study, caseins and methylcellulose (MC) were selected as building materials to prepare a class of mixed gels by adding glucono-δ-lactone (GDL) to induce the gelation of composite MC/casein systems, where the casein concentration was fixed at 8.0% (w/v) and the MC concentration varied from 0 to 1.0% (w/v). It was found that with increasing amount of MC addition (0-0.4%), the mixed gels exhibited a structural conversion from a casein-dominant gel network to a "water-in-water emulsion structure", with the caseins as the continuous gelling phase and the MC as the dispersed phase; further MC addition (0.4-1.0%, w/v) caused a more significant phase separation phenomenon. The structural conversion was in consistent with the determination result of gel hardness. Furthermore, by a combination of confocal laser scanning microscope (CLSM) and rheological studies, the structural evolution process of the mixed gels was revealed to explore the underlying formation mechanism of the mixed gels.