Sorbic acid and potassium sorbate permeability of an edible methylcellulose-palmitic acid film: water activity and pH effects
1991
Rico-Pena, D.C. | Torres, J.A.
The apparent permeability constants for potassium sorbate and sorbic acid through an edible film composed of methylcellulose and palmitic acid (weight ratio 3:1) were evaluated as a function of water activity (aw) and pH. For films with thickness 55-66 micrometers, potassium sorbate permeability increased from 2.3 X 10(-10) to 2.0 X 10(-8) (mg/sec cm2) (cm)/(mg/mL) as aw increased from 0.65 to 0.80. Films were not stable at aw levels above 0.80. Permeability of the film to sorbic acid at aw 0.8 decreased from 3.3 X 10(-8) to 9.1 X 10(-10) (mg/sec cm2) (cm)/(mg/mL) as pH increased from 3 to 7. At pH 3 the undissociated acid was 97.5% and at pH 7 it was 0.4%.
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