Physical, mechanical and transport properties of emulsified films based on alginate with soybean oil: Effects of soybean oil concentration, number of passes and degree of surface crosslinking

Abstract

Edible films and coatings have been applied on fruits to improve their quality during growth and development as well as during postharvest storage. A response surface methodology was used to determine the effects of oil concentration, number of passes and calcium chloride concentration on the physical, mechanical and transport properties of oil-alginate composite films. Alginate-based films were developed using alginate (1.0% w/v), soybean oil (0.5%, 1.0% and 1.5% v/v) and Tween 80® (1% v/v). Coarse emulsions were passed 2, 4 and 6 times through a microfluidizer at 200 MPa. Calcium chloride solutions (0%, 1.5% and 3%) were then applied on the cast films to crosslink them. The oil particle sizes ranged from 360 to 445 nm, regardless of the emulsion composition and number of passes. The lowest water permeability value (1.8857E-10 g/msPa) was obtained for 1.5% oil concentration, 6 passes and no crosslinking. The porosity of the films at low oil concentrations increased with an increase in crosslinking level. In comparison, the porosity of the films at high oil concentrations decreased with an increase in crosslinking level. Emulsified films showed reduced strength and increased elongation with an increase in oil concentration. Films treated with calcium chloride showed lower strength due to greater effects from oil than calcium chloride. In conclusion, oil incorporation in films was the predominant factor in improved film properties, especially for water vapor permeability.