Stability, solubility, mechanical and barrier properties of cassava starch – Carnauba wax edible coatings to preserve fresh-cut apples

This work aimed at evaluating edible coatings/films formulated with cassava starch, glycerol, carnauba wax and stearic acid, analyzing the stability of emulsion (creaming index and lipid particle size), the barrier properties of coatings applied in fresh-cut apples (respiration rate and water vapor resistance), the solubility and mechanical properties of films prepared with coating solutions. A central composite rotatable design 23 was used to select optimized formulation. Independent variables used were: cassava starch concentration (2–4% w/w), glycerol content (1–3% w/w) and carnauba wax: stearic acid ratio (0.0:0.0–0.4:0.6% w/w). The creaming index and the lipid particle size of emulsified coatings were strongly affected by the carnauba wax: fatty acid ratio. Glycerol content was the variable that most influenced the respiration rate of coated apple slices, water vapor resistance of coatings and the elastic modulus of films. The water solubility was positively affected by the cassava starch and glycerol contents. Models and response surfaces were obtained for the respiration rate, water vapor resistance of coatings, elastic modulus and solubility of films. According to statistical analysis results, the optimized conditions corresponded to 3.0 g of cassava starch/100 g of coating solution, 1.5 g of glycerol/100 g of coating solution, 0.2:0.8 g of carnauba wax: stearic acid ratio/100 g of coating solution. The models obtained in the experimental design were predictive, which was evidenced by the relative deviations below 10% in validation procedure.