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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]

Disposable containers made of non-biodegradable polymers are considered as one of the most prevalent environmental pollutants. It is very important and desirable to make fully biodegradable disposable containers for food packaging that does not endanger the health of consumers. In this research, fully biodegradable polymer composites were prepared by melt mixing of polylactic acid (PLA), polybutylene succinate (PBS), and natural polymers including corn starch and wheat straw, and their physical and mechanical properties were evaluated. For this purpose, by conducting experiments according to the optimal custom mixture design of the response surface methodology, the effect of 3 independent variables including the concentration of the PLA and PBS biopolymers blend (50/50% w/w) (CBB) in the range of 30–70, the concentration of corn starch (CCS) in the range of 30–60 and the concentration of wheat straw (CWS) in the range of 0–8 wt percentage of biocomposite on the dependent variables including the elastic modulus (EM), elongation at break (EB), impact strength (IS) and equilibrium moisture content (EMC) of the biocomposite sheet were investigated. According to the results of this research, with the increase in the concentration of corn starch and wheat straw in the studied range, the EM and EMC of the biocomposite increased, while its EB and IS decreased. According to the results obtained from optimizing the effects of independent variables on the physicomechanical properties of the biocomposite sheet, the optimal values predicted by the models for CBB, CCS and CWS were 48.2 wt%, 45.4 wt%, and 6.4 wt%, respectively and predicted values for EM, EB, IS and EMC were 80.8 MPa, 11.4%, 2 kJ/m2 and 4.1%, respectively. Also, the biodegradability rate of the biocomposite with the optimal formulation was 71.1% in the fifth month of the test. • Biocomposites of biopolyester blend filled with two natural polymers were prepared. • Biocomposites contained polylactic acid, polybutylene succinate, starch, and wheat straw. • Constituents concentration had main effects on the sheet's physicomechanical properties. • Optimal sheet contains 48.2 wt% biopolyester blend and 51.8 wt% natural polymers. • The biocomposite sheet with optimal formulation had a high degree of biodegradability. [ABSTRACT FROM AUTHOR]