Effect of osmotic dehydration on the stabilization of calcium-fortified apple slices (var. Granny Smith): Influence of operating variables on process kinetics and compositional changes

Commonly available calcium-fortified foods include non-structured and formulated foods. In contrast, vacuum impregnation allows the introduction of physiologically active compounds to vegetal tissues without disrupting their cellular structure, but inducing changes in their behaviour during further processing. In the particular case of osmotic dehydration of apple slices (var. Granny Smith) with a 55 Brix sucrose solution, both the water loss and the gain in soluble solids were observed to be affected by the amount of calcium incorporated into their porous structure by means of vacuum impregnation, the processing temperature and the addition of 1% of calcium lactate to the osmotic solution. To be precise, water removal was observed to decrease as the calcium content of the vacuum impregnated samples increased from 0% to 40% of the recommended daily allowances for adults in a 200 g sample. Overall, the addition of 1% calcium lactate to the osmotic solution decreased the constant rate of both water loss and gain in soluble solids, but resulted in a final product with an increased mineral content. However, an increase in the temperature of the osmotic solution from 30 to 50 °C was reported to promote faster water loss and soluble solids uptake, but to a different extent depending on the fortification level required for the processed samples. Despite the loss of part of the calcium incorporated to apple slices by means of vacuum impregnation, osmotic dehydration can be considered as a useful tool to increase the stability of this kind of product without seriously reducing its nutritional value.