Impacts of preparation conditions on the structure and emulsifying properties of casein-alginate conjugates produced by transacylation reaction

The Maillard reaction is often used to glycate proteins but produces undesirable byproducts. In this study, the transacylation reaction was used for the first time to prepare protein-polysaccharide conjugates from sodium caseinate (NaCas) and propylene glycol alginate (PGA) as novel emulsifiers. By mixing NaCas and PGA (1% w/v) at mass ratios of 1:2, 1:1, and 2:1 for 2 h with pH maintained at 11.0, NaCas-alginate conjugates with 52.8%, 66.2%, and 76.5% NaCas were prepared, respectively. The purified conjugates resulted in the preparation of oil-in-water emulsions with a low surfactant-to-oil ratio of 0.75:100 (w:v), and the resultant emulsions were stable against environmental stresses of pH, ionic strength, and thermal pasteurization. Structural analyses showed the role of NaCas content in reducing droplet size and the role of the alginate moiety stabilizing oil droplets via the electrostatic and steric mechanisms. This work may be significant to prepare protein-polysaccharide conjugates with high emulsifying capacity and tunable functionalities using a scalable and green method.

Automated summary

The transacylation reaction was used to prepare protein-polysaccharide conjugates as emulsifiers, which were able to stabilize oil-in-water emulsions. The NaCas content reduced droplet size, while the alginate moiety stabilized oil droplets via electrostatic and steric mechanisms.