Developing an emulsion model system containing canthaxanthin biosynthesized by Dietzia natronolimnaea HS-1

An acceptable strategy to incorporate canthaxanthin (CX) as a natural colorant into products is by means of oil-in-water emulsions. The used CX in this study was produced by bacterium Dietzia natronolimnaea HS-1 using a batch bioreactor system. A central composite rotatable design-response surface methodology (CCRD-RSM) consisting of three-factored factorial design with five levels was applied for analysis of the results to obtain the optimal formulation of emulsions. Three independent variables including fenugreek gum (FG, 0.2-0.5%, w/w), coconut oil (CO, 6-10%, w/w), and CO/CX ratio (10:1-50:1) were transformed to coded values and second-order polynomial models was developed to predict the responses (p < 0.0001). The studied independent variables were the stability, viscosity and droplet size properties such as volume-weighted mean diameter (D43), specific surface area (Sv) and polydispersity index (PDI) of emulsions. The 3-D response surface plot derived from the mathematical models was used to determine the optimal conditions. Main emulsion components under the optimum conditions ascertained presently by RSM: 50:1 CO/CX ratio, 0.49% (w/w) FG content and 6.28% (w/w) CO concentration. At this optimum point, stability, viscosity, D43, Sv and PDI were 90.6%, 0.0118 Pa s, 0.595 μm, 12.03 m2/ml and 1.380, respectively.