Influence of vacuum treatment on mass transfer during osmotic dehydration of fruits

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Abstract

Three kinds of fruits—apricots, strawberries and pineapples — have been studied as experimental material to analyse the influence of operating pressure of osmotic dehydration on the mass transfer rate in fruits. The experiments were carried out in 65 °Brix sucrose solution at 30–50 °C for 15–240 min under normal pressure, vacuum and pulse vacuum treatments, respectively. The experimental results revealed that the vacuum treatments increased water transfer rate, but had no effect on sugar uptake between vacuum and normal pressure treatments during osmotic dehydration. The influence of the vacuum treatments on water loss was more effective for pineapples because of their higher porosity. The porosity coefficient of fruits can be used as an indication of the suitability of fruits for vacuum treatment. The pulse vacuum treatment is highly recommended due to its economical advantages and satisfactory water loss. Equations based on diffusion and osmosis kinetics for mass transfer were used to analyse the experimental results.

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