Abstract: In this study, whey protein isolate (WPI) and theanionic polysaccharide xanthan gum (XG) were used as basic raw materials to prepare composite particles. To explore the main factors that affect the formation of composite particles, the effects of preparation conditions such as ionic strength, temperature, and mixing mode on the turbidity, particle size, and zeta potential of the WPI-XG composite system, and the structure of the particles through a laser confocal microscope. The results showed that low ionic strength (≤ 20 mmol/L) could promote the formation of WPI-XG composites; the higher the temperature, the larger the particle size of the composite particles. The particles prepared by heating the WPI solution and then mixing it with the XG solution had larger protein-to-polysaccharide ratio, smaller particle size and greater absolute value of zeta potential; in contrast, shearing could decrease the particle size and the absolute value of zeta potential. Finally, it is concluded that the sheared WPI particles subjected to heat treatment at 75 ℃ and XG could form a more complete “core-shell” structure.

Key words: whey protein isolate; xanthan gum; composite particles; particle size; microstructure