The interaction between casein and hydroxypropyl distarch phosphate (HPDSP) in yoghurt system

The hydroxypropyl distarch phosphate (HPDSP) was added to set yoghurt system as stabilizer in present work. Herein, the interaction between casein and HPDSP was researched. During the course of the study, casein and modified starch were placed in a simulation yoghurt environment in order to facilitate the observation and research. Light microscope and atomic force microscope (AFM) were applied to observe the microstructure of the samples. Results revealed that the aggregate degree of protein was decreased with adding HPDSP. The AFM micrograph proved that some protein particle adsorption on the surface of starch granule at pH 3.8. Dynamic light scattering (DLS) measurement indicated that particle size decreased with the concentration of modified starch increasing. Through zeta potential measurement, we hold opinion that casein particles absorb on the surface of the HPDSP via electrostatic forces. The research shows that the stability of modified starch is the result of “electrostatic repulsion” and “steric stabilization”. AFM 3D image and 2D image of samples. (A): HPDSP without casein at pH 3.8. Scan size: 10 μm × 10 μm, height scale: 271 nm (B): Starch area of mixed solution at pH 3.8. Scan size: 3 μm × 3 μm, height scale: 59.1 nm. [Display omitted] •The effect of hydroxypropyl distarch phosphate on the set yoghurt system was studied.•Some protein particle adsorption on the surface of starch granule at pH 3.8.•The particle size decreased with the increasing of modified starch concentration.•The casein particles absorb on the surface of the HPDSP via electrostatic forces.