Effect of osmotic dehydration on the dielectric properties of carrots and strawberries

Osmotic dehydration can be used as a pretreatment for microwave drying. Since microwave drying is dependent on the dielectric properties of the material to be dried, it is important to know if osmotic dehydration has any effect on these properties. Strawberries and Car-rots were used in this study. Two osmotic agents, sucrose and salt, were used for carrots but only sucrose was used for strawberries. The effects of variations in sucrose and salt concentrations, solution temperature, and length of immersion time on the dielectric constant (epsilon') and the loss factor (epsilon '') were measured. A predictive model was established for the range of variation used for each of the conditions studied. In general, the epsilon' decreased with an increase in osmotic conditions. The epsilon '' of strawberries was not affected by osmotic dehydrations. The use of salt as the osmotic agent did have a significant effect on the epsilon '' of carrots. Predictive models of dielectric properties of strawberries and carrots were developed using response surface methodology. (C) 2008 Elsevier Ltd. All rights reserved.