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Abstract The objective of this study was to evaluate cornstarch nanocrystals (CSNC) suspensions (10, 12 and 14%) as a fat replacer in reduced fat emulsions (25% fat reduced: 25FR, 50% fat reduced: 50FR and 75%fat reduced: 75FR). Atomic force microscopy (AFM) showed rounded edge platelet-like particles with size around 10–150 nm. Sulfate content and zeta potential of CSNC were 0.21% and −34.6 mV, respectively. Nanocrystals crystallinity (36.8%) was higher than the source starch (25.7%). Rheological and physical properties of reduced fat emulsions were compared to full-fat emulsion (control, 80% fat). All the emulsions indicated good homogeneity (PDI = 0.21–0.29). There was no significant difference between the Z-average of the control and some samples (25FR with 14% CSNC, 50FR with 12% CSNC and 75FR with 10–12% CSNC). The reduced fat emulsions showed higher absolute zeta potential values (33.2–39.4 mV) than control (31.9 mV), resulting from the negatively charged surface of CSNC. Although the full-fat emulsion revealed the highest whiteness index (99.27), no significant changes were observed at the low levels of fat reduction and CSNC substitution. On the basis of dynamic rheological properties, the emulsions indicated a more solid like behavior as a result of fat reduction and CSNC addition, related to smaller droplet size and more negative charges. The reduced fat samples had more spreadability than the control. The results indicated a probable formation of nanocrystal network in the continuous phase, which trapped the oil droplets and prevented creaming after 6-month storage. Graphical abstract Image 1 Highlights • Reducing fat and adding CSNC led to smaller droplet size and more zeta potential. • The ability of CSNC to strengthen the structure was affirmed by rheological data. • All reduced fat emulsions showed more solid-like behavior than full fat sample. • No creaming was observed for all studied emulsions after 6-month storage. • Higher spreadability was obtained as fat reduction and CSNC levels increased. [ABSTRACT FROM AUTHOR]

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 496 nm and from 149 to 234 nm, respectively. However, no creaming is observed for each sample throughout the storage time. [ABSTRACT FROM AUTHOR]