Release of Calcium Benzoate from Films of Sodium Alginate Crosslinked with Calcium Ions

Alginate-based biofilms were reticulated with Ca++ supplied by two sources, calcium chloride and benzoate, and using glycerol as plasticizer. The strong gelling power of the Ca++ ions hindered smooth casting procedures, so that films with low degree of reticulation were initially manufactured (1(st) stage). These films were further crosslinked with an excess of Ca++ by immersion in a solution of 3 to 7% of CaCl2 center dot 2H(2)O(2(nd) stage). The release of sorbate was evaluated considering different active agent concentrations in the film and two levels of alginate crosslinking. The mechanism involved in the diffusional process was investigated using the Power Law Model. The results indicated that potassium sorbate diffusion in alginate films has characteristics of Fickian and non-Fickian behavior. Effective diffusion coefficients obtained using the solution in series derived from Fick's Second Law are close to values obtained with the short-time solution, with effective diffusivities varying from 3 to 5 x 10(-7) cm(2)/s. The diffusivity values decreased with the degree of reticulation and increase with benzoate concentration in the film.