Calcium alginate films: thermal properties and permeability to sorbate and ascorbate

ABSTRACT Calcium alginate films were prepared by the pH‐controlled release of calcium ions into alginate solution or by the cooling of hot calcium alginate gels. Thermogravimetry and calorimetry showed that the controlled Ca release films contained a greater amount of high‐temperature component, and required extra energy to dissociate the tightly crosslinked calcium alginate. Structural differences were reflected by the permeability of the two films to potassium sorbate: 1.06 × 10–7 (controlled Ca release) and 1.58 × 10–7 cm2sec–1 (cooled). Apparent activation energy was estimated to be for the diffusion of potassium sorbate 24.1 KJ·mol–1, sodium ascorbate 23.7, and ascorbic acid 36.2. Results suggested that the pH of the diffusant solution had an interactive effect on the alginate film.