Schiff base type casein-konjac glucomannan conjugates with improved stability and emulsifying properties via mild covalent cross-linking

Casein (CAS)-stabilized emulsions are susceptible to destabilization by environmental influences and could be improved by introducing polysaccharides (PS). The binding mode and interaction between PS and CAS also have a great influence on the emulsifying property of their complexes. Therefore, this study covalently combined dialdehyde konjac glucomannan (DAK) with CAS via mild covalent cross-linking, and the capacity of CAS-DAK to stabilize oil-in-water emulsion was investigated. The results showed that the covalent combination between DAK and CAS increased the emulsifying property and stability of CAS by 46.94% and 12.83%, respectively. At low solid concentrations (0.2–1.2%, w/v), the CAS-DAK stabilized emulsions with droplet sizes ranging from 9.43 ± 0.10 μm to 28.95 ± 0.06 μm, with which the emulsification index being mainly influenced by the conjugate concentration and oil content. At an oil phase fraction of 0.70–0.80, CAS-DAK stabilized emulsions showed a lower creaming index, higher viscosity, and lower Turbiscan stability index and exhibited elastic gel-like rheological properties. In conclusion, the covalent cross-linking of DAK with CAS at low temperatures can significantly enhance the emulsification and emulsion stability of CAS, which may contribute to the development of new food-grade protein-polysaccharide conjugate stabilized emulsions and provide a theoretical basis for their application in the food industry.