Effect of the impregnated solute on air drying and rehydration of apple slices (cv. Granny Smith)

Apple (cv. Granny Smith) slices (8 mm thickness, 20 mm internal diameter, 64 mm external diameter) were vacuum impregnated with solutions of glucose, sucrose and trehalose. These were hot air dried and rehydrated in solutions of the same solutes. For impregnating solutions, aw was 0.96 whereas for rehydration aw was 0.99. Throughout dehydration (45 °C) the water effective diffusion coefficient in the product’s liquid phase (De) was determined. This was lower in sucrose and trehalose impregnated samples. Throughout rehydration (25 °C, 8 h), water gain, solute loss and compositional changes were quantified. Peleg’s equation accurately described the mass and water gain, solute loss and compositional changes. Glucose impregnated slices showed the greatest mass recovery, whereas those treated with disaccharides showed less solute leaching during rehydration and better liquid phase retention during centrifugation. These results point to particular interactions of the impregnated solutes with the fruit matrix, giving rise to quality changes in the dried product.