A two-parameter equation was developed from mass balance considerations and used to predict the kinetics of osmotic dehydration and the final equilibrium point. The model was tested using kinetic data from ten different experiments and was able to predict water loss and solids gained over long periods of drying. The final equilibrium point was estimated using data obtained during a relatively short period of time. Simple equations were obtained when the model was related to Fick's second law for non-steady one-dimensional diffusion through a thin slab, and apparent diffusion coefficients were readily estimated from these equations.

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Mesquite gum solutions (30% w/v) were used to emulsify orange peel oil in an oil-gum solids ratio of 0.25. Emulsions were spray dried in laboratory scale equipment. The powders were stored in a w (s) from 0.108 to 0.743 at 35 Њ Њ Њ Њ ЊC. Quantitative analysis of limonene oxide indicated that the sample at 0.628 showed a very good stability against oxidation after thirty d, without caking and stickiness occurring. At this water activity the system was within rubbery state, and the moisture content corresponded to that of the minimum integral entropy.

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The effect of temperature (30, 40 and 50°C) and sucrose concentration (50, 60 and 70"Brix) on the osmotic dehydration of commercial size pineapple rings were studied, at an initial ratio of 1:4 fruit:sucrose solution. The rate of water loss in the fruit varied with both osmotic solution concentration and temperature. A proposed model based on Crank's equation was fitted to the experimental data.

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