Structural characteristics of gluconic acid δ-lactone induced casein gels as regulated by gellan gum incorporation

The co-gelation phenomenon of caseins and gellan in yogurt-related products is usually observed, highlighting the possibility of developing mixed casein/gellan systems as a new type of food gels. In this study, mixed gellan/casein gels were prepared by adding different amounts of gluconic acid 6-lactone (GDL) to acidify gellan/casein mixtures at a fixed casein concentration (8.0%, w/v) and varying gellan concentrations (0-0.6%, w/v). It was found that both the gellan concentration and the GDL addition amount affected the gel microstructures and gel strength; with increasing gellan concentration, the mixed systems gradually exhibited a significant phase separation, accompanied by a structural transition from homogeneous, casein-dominant gel structure to a water-inwater emulsion structure (where the casein-enriched phase acted as the continuous phase and the gellanenriched phase as the dispersed phase). A higher level of GDL addition slightly retarded but did not abolish the phase separation by inducing a quicker gelation process. Moreover, based on the prepared gel matrices, composite gellan/casein emulsion gels were successfully developed. Conclusively, our results indicate that gellan can be used to regulate the microstructures of casein-based gels, which may further pinpoint the possibility of using mixed gellan/casein systems to diversify food gel design strategies.

Automated summary

The study showed that both gellan concentration and GDL addition amount affected the microstructures and gel strength of the mixed gellan/casein gels, with higher gellan concentration leading to phase separation and GDL slightly retarding but not abolishing the phase separation.