Effect of Ca²⁺ induced crosslinking on the mechanical and barrier properties of cast alginate films

The use of alginate as a coating material for packaging applications is currently limited due to its difficult processability and high moisture sensitivity. Therefore, this study addresses the crosslinking and scale‐up to a continuous application. Three different crosslinking agents were applied: CaCl 2 with ethylene diamine tetraacetic acid and two low soluble salts (CaHPO 4 and CaCO 3 ). Those were incorporated by internal setting in an alginate matrix with varying Ca 2+ concentration ( ) and ratio. With the addition of Ca 2+ , the tensile strength and elongation at break of the cast alginate films increased. This was optimal for a of 0.010–0.015 g (g alginate) −1 dependent on the crosslinking agent. The decrease in water vapor and oxygen permeability due to crosslinking was independent of the crosslinking agent. However, the optimal aiming to decrease permeability was different for the crosslinking agents: CaHPO 4 showed best results at a of 0.010 g (g alginate) −1 , CaCl 2 at 0.012 g (g alginate) −1 , and CaCO 3 at 0.027 g (g alginate) −1 . Upon all analyzed properties CaHPO 4 was the most promising crosslinking agent for alginate. Moreover, selected alginate formulations were successfully processed in a continuous lacquering plant. The produced two‐layer systems have very low oxygen permeabilities which can be further reduced by crosslinking.