WATER-VAPOR PERMEABILITY OF CASEINATE-BASED EDIBLE FILMS AS AFFECTED BY PH, CALCIUM CROSS-LINKING AND LIPID-CONTENT

Edible films were cast from solutions of sodium or calcium caseinate and from emulsions of these proteins with acetylated monoglyceride, beeswax, and stearic acid. The water vapor permeabilities of the films were evaluated at 25-degrees-C using the ASTM E96-80 method, modified to calculate the % relative humidity at the film underside. Adjustment to pH 4.6 (isoelectric point), calcium ion crosslinking and combined effects of calcium ascorbate buffer (pH 4.6) reduced water vapor permeability of sodium caseinate films by 36%, 42%, and 43%, respectively. Calcium caseinate-beeswax emulsion films had water vapor permeabilities up to 90% lower than pure sodium caseinate films. Water vapor permeability varied by a factor of two depending on emulsion film orientation, indicating nonisotropic structure.