In this study, a face central composite design (FCCD) is applied to optimize the formulation of reduced fat o/w emulsions containing cornstarch nanocrystal (CSNC) as a novel fat replacer. Data analysis shows that independent variables including fat replacement levels (25, 50, and 75%) and CSNC concentration (10, 12, and 14%) significantly (p<0.05) affect all responses. In this regard, increases in the levels of both fat replacement and CSNC decrease the droplet size and increase the values of yield stress, elastic modulus at 1 Hz, slope of tan delta at non-linear viscoelastic region and degree of thixotropy, indicating a stronger gel network formed. Numerical optimization is used to determine the optimum formulation of the reduced fat emulsion based on properties of a full-fat emulsion. This optimum point is estimated to be 47.80% of fat replacement and 11.99% of CSNC concentration. Closeness between the experimental and predicted values of the studied characteristics demonstrates the suitability of the corresponding models. Furthermore, the storage of full-fat and optimum reduced-fat emulsions at 4 C for one month leads to an increase in droplet size from 144 to 496nm and from 149 to 234 nm, respectively. However, no creaming is observed for each sample throughout the storage time.
