Sorbic Acid and Potassium Sorbate Permeability of an Edible Methylcellulose-Palmitic Acid Film: Water Activity and pH Effects

Authors

  • DELMY C. RICO-PEÑA,

    1. Author Torres is affiliated with the Food Engineering Group, Dept. of Food Science & Technology, Oregon State Univ., Corvallis, OR 97331. Author Rico-Peña is now with Escuela de In-geniería Quimica, Universidad de El Salvador, San Salvador, El Salvador.
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  • J. ANTONIO TORRES

    1. Author Torres is affiliated with the Food Engineering Group, Dept. of Food Science & Technology, Oregon State Univ., Corvallis, OR 97331. Author Rico-Peña is now with Escuela de In-geniería Quimica, Universidad de El Salvador, San Salvador, El Salvador.
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  • Oregon State Univ. Experiment Station Publication No. 9122.

  • Author Rico-Peña gratefully acknowledges support from the Fulbright-Latin American Scholarship Program of American Universities (LASPAU) and the Universidad de El Salvador.

ABSTRACT

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 μm, potassium sorbate permeability increased from 2.3 × 10−10 to 2.0 × 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 × 10−8 to 9.1 × 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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