A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Food Engineering and Bioprocess Technology

Thesis (M. Sc.) - Asian Institute of Technology, 2018

This study aims to evaluate the effects of whey protein isolate (WPI) and xanthan gum (XG) stabilized oil-in-water emulsions loaded with astaxanthin for their physicochemical stability and in-vitro gastrointestinal tract behavior. The formulations of emulsions with different WI and XG concentrations were evaluated. Whey protein isolate concentration was varied from 2 to 5 wt%, while XG was varied from 0 to 0.5 wt%. The result showed that the additions of 0.5 wt% XG with all different WPI concentrations increased the viscosity, reduce creaming and the phase separations. Furthermore, the emulsion with 0.5 wt% XG did not exhibit any phase separation during the storage period of 30 days. The astaxanthin-loaded emulsions were further evaluated for the influences of temperature, pH, ionic concentration and light. Emulsions were found physically stable up to 70 °C. The retention of astaxanthin after processing conditions based on pasteurization was determined at 63 °C and 72 °C under different intervals of time. The retention of astaxanthin was around 80% after heating at 63 °C during 15, 30 and 45 min. However, the highest astaxanthin retention (98%) was found under 72 °C for 15 min. The emulsions were not stable at pH 2-4. Furthermore, emulsions were found physically stable under the different salt concentrations, in the ranges of 0-150 mM. The astaxanthin retention of emulsion exposure to light condition is 78% over 32 h. Additional, emulsions with WPI and WPI+XG were assessed through an in-vitro gastrointestinal model and changes in their particle size, zeta potential were evaluated. The bioaccessibility of astaxanthin incorporated into PI-stabilized emulsion and emulsion with WPI+AG is 46.2 % and 12.6 % respectively.