Effect of Temperature on the Moisture Sorption Isotherms and Water Activity Shift of Two Dehydrated Foods

Authors:
  • TLT. P. Labuza
    T. P. Labuza
  • AKA. Kaanane
    A. Kaanane
  • JCJ. Y. Chen
    J. Y. Chen
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Abstract
The water activity (a w ) of eight salt solutions was determined at three temperatures (25, 30, 45°C) using a pressure transducer‐vapor pressure manometer. The a w s of the salts showed a decrease with increasing temperature, which was explained with the help of a thermodynamic equation. This is opposite to the increase in a w with increase in temperature for foods. Moisture sorption data for fish flour and cornmeal were obtained at 25–65°C. The Guggenheim‐Anderson‐deBoer model was evaluated and shown to be comparable to the Brunauer‐Emmett‐Teller model for prediction of the monolayer. Product was equilibrated at different a w s at 25°C then subsequently shifted to 30°C and 45°C in a sealed chamber. The resultant a, change, measured on the Kaymont‐Rotronics, was predictable from the isotherm at each temperature using the Clausius Clapeyron relationship.

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