An experimental method to measure the effective diffusivity of chemical substances through the skin (exocarp) of fruits and vegetables is described. A circular disk of skin was placed in a specially constructed diffusion cell to separate two flowing solutions. Changes in conxentration with time were monitored and the diffusion properties were estimated from Fick's diffusion equation. The calculations were based on results taken either in the early transient period or in the late period of steady-state flow. The method and the design of the diffusion cell allowed measurements with negligible edge effects and rapid detection of errors due to leaks or contamination. Diffusion characteristics were determined for the penetration and movement of sodium hydroxide through the skins of tomatoes and pimiento peppers. The diffusivity through tomato skin was 2·0 × 10-8cm2s-1and through pimiento pepper skin 5·5 × 10-8cm2s-1at 72°C. Results were reproducible and agreed with previous studies. © 1989.
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