Effect of sugar type and concentration on the heat coagulation of oil-in-water emulsions stabilized by milk-protein-concentrate

The influence of various sugars, on the heat stability of a milk-protein-concentrate (MPC)-stabilized emulsion (10% w/w protein, 10% w/w oil) was studied. Regardless of concentration, the addition of sugars during emulsification slightly increased the droplet diameter except the addition of 20–30% w/w maltodextrin significantly (p < 0.05) decreased the droplet diameter and was attributed to the larger change in disperse/continuous phase viscosity ratio. Generally, the addition of sugar reduced the heat coagulation time (HCT) determined at 140 °C. The increased concentration of glucose, maltose, sucrose, trehalose shifted the pH at heat stability maximum towards more acidic values whereas the increased concentration of maltodextrin shifted the pH at heat stability maximum towards more alkaline values. The extent of destabilization also varied between sugars, with trehalose being particularly effective in retaining the original heat stability of the MPC-stabilized emulsions. Reducing sugars (glucose, maltose, maltodextrin) decreased the heat stability maximum more significantly than non-reducing sugars (sucrose and trehalose). Particle size, microstructure, and rheological measurements showed good correlations with the heat stability. Several factors, including free calcium ion level, volume fraction of the continuous phase protein and solvent quality, will also affect the heat stability of MPC-stabilized emulsions with added sugars.