Fabrication of whey protein isolate/chitosan complexes and its protective effect on allicin

Whey protein isolate (WPI) and chitosan (CS) complexes were prepared by complex coacervation method. The effects of different WPI/CS ratios and pH values on the formation of complexes were investigated. And then the protective effect of the WPI/CS complexes on allicin was further analyzed. The turbidity, particle size and zeta potential data showed that optimum soluble complex coacervation occurred at pH 5.0 when the WPI/CS ratio was 4:1. Electrostatic interaction and hydrogen bonding were the main driving forces involved in the coacervation. Changes in differential scanning calorimetry (DSC) curves indicated that WPI/CS complexes exhibited higher thermal denaturation temperature than WPI. The retention ratio of encapsulated allicin was 71.4% after stored at 4 degrees C for 14 weeks, which was increased by 51.6% as compared with that of free allicin. Due to the denaturation of protein, a high-temperature (90 degrees C) and long-time (7 h) treatment would result in a decrease of stability for encapsulated allicin. Results of this study would be helpful for designing food particles, which can be used for encapsulation and protection of bioactive molecules under certain conditions.