Adsorption of Volatile Organic Compounds in Dehydrated Food Systems. 1. Measurement of Sorption Isotherms at Low Water Activities

Abstract

SUMMARY Removal of water vapor during food dehydration results in losses of volatile compounds that contribute to flavor. The relative importance of diffusion and adsorption to retention of volatile components by solid food constituents during dehydration processes is not well known. A frontal analysis gas chromatographic apparatus has been developed to measure vapor‐solid adsorption at low adsorbate concentrations. Volatile compound is sorbed from the gas stream by an adsorbent in a system designed to minimize diffusion and kinetic effects. The system includes saturator chambers, which maintain constant concentration of adsorbate in the carrier gas stream, and a flame ionization detector. Data collected are presented as sorption isotherms. With microcrystalline cellulose powder as adsorbent and hexane and acetone vapors as adsorbates partial pressures in the range of 1 millitorr were produced and maintained. Resulting concentrations measured were in the range of micrograms adsorbate per gram adsorbent (ppm), orders of magnitude encountered in real dehydrated food systems.