Air drying kinetics and quality characteristics of osmodehydrated-candied pumpkins using alternative sweeteners

Abstract

In order to obtain nutritious, low calorie candied pumpkins, of superior quality, air drying kinetics of pretreated pumpkin slices were investigated using three different drying temperatures (40, 60 & 80 °C). Before drying, pumpkins were osmotically treated using different osmotic agents, namely sucrose, oligofructose and their mixture (1:1) in a solution of a constant concentration (70°Brix), at three temperature (75, 85 & 95 °C) for 150 min. Changes in texture (hardness and compression work) were determined during drying and sensory characteristics of the final products were evaluated by trained panelists. A first-order reaction kinetic model was used to predict the drying rate and hardness, in which the rate constant was a function of the process temperature. The results showed that as the drying temperature is increased, the drying constant also increases whereas the equilibrium moisture content of the dehydrated products decreases. The hardness of candied pumpkins was mostly affected by the air drying temperature regardless the osmotic dehydration conditions. Sensory evaluation of the final candied pumpkins, showed a preference for the products osmotically treated by oligofructose.

Keywords:

• Candying
• drying kinetics
• oligofructose
• osmotic dehydration
• pumpkin
• texture

Acknowledgements

The authors wish to thank Prof. Evangelos S. Lazos for support and useful discussions.