Influence of osmotic dehydration process parameters on the quality of candied pumpkins

• Influence of the osmodehydration process on candied pumpkins quality was studied.
• Mass balance equations based on Fick's second law were solved numerically.
• Effective diffusion coefficients of water and sucrose increase with temperature.
• Harder and less elastic products were obtained with increasing sucrose content.
• Rheological changes were related with the reinforcement of the cell wall matrix.

The influence of osmotic dehydration process parameters on the efficiency of water loss and sucrose gain of pumpkins and the influence on the quality of the final product are essential for production of superior quality candied pumpkins. Mass transfer kinetics during osmotic dehydration of pumpkins were modelled by assuming Fickian diffusion of sucrose and water in unsteady state conditions, which described very well the experimental results for water loss and sugar gain. Water and sucrose effective diffusion coefficients increase significantly with temperature. Temperature and sucrose concentration had a significant influence on both water and sugar diffusion, increasing as the solution temperature increased. Significant increase in the effective water diffusivity and decrease in the sucrose effective diffusivity was observed when the sucrose solution concentration increased from 40 °Brix to 50 and 60 °Brix. From 50 to 60 °Brix, no difference in the effective diffusivities was observed. Candied pumpkins with higher sucrose content have a higher breaking stress, less breaking strain and lower work to fracture. Moreover, the product becomes harder and less elastic with increasing sucrose content, resulting in more brittle products, which seems to be related with reinforcement of the pumpkin cell wall matrix.