Effect of osmotic pre-treatment and infrared radiation on drying rate and color changes during drying of potato and pineapple

A combination of intermittent infrared and continuous convection heating was used to dry various osmotically pretreated sample of potato (in solutions of 10%, 20% and 30% NaCl) and pineapple (in solutions of 30%, 50%, 70% Brix). The effect of drying conditions on color changes of potato and pineapple was investigated. The Hunter color scale parameters (redness, yellowness and lightness) were measured to quantify the color changes. With appropriate choice of infrared intermittency as well as osmotic pretreatment, it is possible to reduce the overall color change while maintaining high drying rates. As expected, osmotic pretreatment resulted in a shift in the sorption isotherms for both products.