Physical and mechanical properties of sago starch – alginate films incorporated with calcium chloride

Edible films were prepared from sago starch: alginate mixtures with ratios of 1:0, 4:1, 3:1, 2:1, 1:1 and 0:1. The physical and mechanical properties of films were modified with the addition of calcium chloride (CaCl2) (2 x 10^4 mg/kg) in the film solutions and by immersion of the films into a CaCl2 (2% w/w) solution. The films were characterized for tensile strength (TS), percentage of elongation at break (% E), calcium content and water solubility (WS). The calcium content in 100% alginate films was significantly higher compared to those after immersion for 1 min in a CaCl2 solution. Immersion of films into a CaCl2 solution for 1 min increased the TS, except for 100% sago starch film. Prolonging the immersion time for 10 minutes did not significantly affect the TS of the films. Moreover, increasing the immersion time did not significantly decrease the WS of the films. Addition of CaCl2 in film solutions with higher ratios of alginate significantly increased their TS and % E. Films treated with CaCl2 by the immersion process led to markedly increased TS compared to those treated by CaCl2 addition in the film solutions.