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

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