Effects of alginate-glycerol-citric acid concentrations on selected physical, mechanical, and barrier properties of papaya puree-based edible films and coatings, as evaluated by response surface methodology

The development of edible coatings is an interesting strategy to reduce the use of conventional packaging materials and extend the shelf life of minimally processed fruits. The potential of papaya puree (PP) as a base for formulating edible films and coatings containing alginate (0.5-1.0 g/100 mL), glycerol (0.8-1.5 g/100 mL), and citric acid (0.5-1.0 g/100 mL) was evaluated. A Box-Behnken experimental design was used to determine the effect of independent variables on selected physical and mechanical properties, water vapor permeability (WVP) of PP edible films (PPEFs), and the surface solid density (SSD) and water vapor resistance of PP coating solutions (PPCSs) applied to papaya cubes. Furthermore, the PPEFs and PPCSs were optimized and validated using response surface models. Alginate-citric acid and glycerol-citric acid interactions significantly affected the SSD. The highest puncture strength of PPEFs was 17.94 MPa, with the highest concentration of alginate, whereas the WVP increased with higher concentrations of glycerol and citric acid. The optimum concentrations of alginate, glycerol, and citric acid for PPCSs and PPEFs were predicted to be 0.50, 1.32, and 0.59 g/100 mL, and 0.78, 0.80, and 0.50 g/100 mL, respectively. The mean average relative percent deviations between the experimental and predicted values were less than 10%.