Mechanical and physical properties of calcium-treated gellan films

The physicochemical properties of Ca2+-treated gellan films plasticized with glycerol were investigated as a function of CaCl2 concentration (0–20%, w/w) in an aqueous soaking solution. Films were examined based on their mechanical properties, water vapor permeability (WVP), swelling index (SI), thickness and opacity. The SI was lower for Ca2+-treated films relative to a control, however, above 13% (w/w) CaCl2 no differences in SI were found. At 13% (w/w) CaCl2, tensile and puncture strengths reached a maximum. Tensile elongation, puncture deformation, film thickness and WVP were lower for CaCl2-treated films than untreated, however, all increased with CaCl2 concentration. Opacity of gellan films increased with the Ca2+-treatment relative to the untreated film, however declined as CaCl2 concentration increased. In general, Ca2+-treated gellan films were stronger, acted as better water vapor barriers, swelled less when in contact with water, and became less pliable and transparent.