Evaluation of rheological and optical properties plus stability of beverage cloud emulsions prepared with corn oil, gum rosin, and modified starch.

Abstract

Rheological and optical properties as well as stability of beverage cloud emulsion prepared with corn oil, gum rosin (EG), and modified starch were evaluated in model juices. The emulsions were prepared with three levels of modified starch (6%, 12%, and 18% w/w), corn oil (5%, 7%, and 9% w/w), and gum rosin (1%, 3%, and 5% w/w). Experiments were designed using the Box-Behnken design. The analysis of variance (ANOVA) was used to evaluate the significance of the experimental factors and the factors were then optimized using response surface methodology (RSM). The stability of emulsions was measured through ring formation in both the primary emulsion and the model beverage as a function of storage time. Also, the effect of heat treatment was examined on the stability of emulsions in model beverages. The results revealed that heat treatment did not cause the formation of an observable ring in the model juice containing stabilized starch emulsion. Rheological examinations of the stable emulsion samples showed a pseudoplastic and time-independent non-Newtonian behavior. The optimum emulsion sample consistency coefficient was 0.46 Pa.sn and the flow behavior index was 0.88. The apparent viscosity of the optimum emulsion sample based on Herschel-Bulkley model at shear rate of 100 s-1 was 0.0439 Pa.s. The results indicated that the concentration of modified starch, gum rosin, and corn oil has a significant effect on the stability and creaminess of the emulsion. In general, with an increase in the percentage of modified starch, the stability rises while the rate of creaminess decreases (p < 0.05). Furthermore, elevation of the concentration of corn oil had a significant effect on the opacity of emulsions and the final product (p < 0.05).