Effect of Surface Density on the Engineering Properties of High Methoxyl Pectin-Based Edible Films

The effect of pectin surface density (ρ _s) on the engineering properties of high methoxyl (HM) pectin-based edible films was determined in order to explore the role of ρ _s on structure and functional properties. Films at different ρ _s values (2.5, 3.2, 3.8, 4.5, 5.1, 5.8 mg cm⁻²) were analyzed by means of microscopy, thermal, mechanical, and barrier (water vapor permeability WVP, oxygen permeability \textkP_\textO2 {\text{kP}}_{{{\text{O}}_2 }} , carbon dioxide permeability \textkP_\textCO2 {\text{kP}}_{{{\text{CO}}_2 }} ) properties. Microscopy, thermal, and mechanical results showed that by increasing ρ _s from 2.5 to 5.8 mg cm⁻², the film structure does not change. HM pectin-based film has a tensile strength of 20 ± 7 MPa and an elastic modulus (E) equal to 2,400 ± 200 MPa. However, it is quite brittle as the elongation to break (e) is close to 1%. Although the film structure was unaffected by ρ _s, WVP increased with the rise in ρ _s while \textkP_\textO2 {\text{kP}}_{{{\text{O}}_2 }} and \textkP_\textCO2 {\text{kP}}_{{{\text{CO}}_2 }} decreased. On the whole, HM pectin-based film showed barrier properties comparable to biodegradable commercial film and low selectivity.