Osmotic dehydration with sorbitol combined with hot air convective drying of apple cubes.

The aim of the present work was to study the effect of the osmotic dehydration (OD) pre-treatment on the mass transfer kinetics and water activity (a) of apple cubes during hot air drying. The adequacy of different mathematical models to describe the moisture content of the product during this process was also evaluated. Apple cubes were osmotically dehydrated with sucrose or sorbitol solutions at 60 °C, and then dried by air at 25-80 °C. Overall, the OD and rise of the air temperature resulted in an increased water loss rate and a reduction of the a. The osmotic agent used in the OD was not relevant to the air drying kinetics, but the pre-treatment with sorbitol solutions produced dried samples with lower a. Newton's, Page's, modified Page's, Henderson and Pabis', Two-term, Two-term exponential, Logarithmic, Midilli et al.'s models could describe the moisture content well during the air drying process.