Osmo-frozen fruits: mass transfer and quality evaluation

The quality of osmofrozen pears, kiwis, strawberries and apples was studied through measurements of colour, drip-loss and texture after each step of the combined process, that is, after osmotic dehydration for different periods of time and after freezing in a conventional air-blast tunnel at −40 °C. The results were compared to those obtained for fresh products. The effect of the osmotic solution on the whole process has also been investigated using different osmotic solutions (sucrose, glucose and corn syrup mixtures). The evolution of mass transfer was measured through the variation in time of weight loss and the solid gain. The osmotic dehydration prior to freezing demonstrated to be useful for limiting drip loss and, in some cases, to decrease colour change and improve texture. The choice of the dehydrating agent and the usefulness of the pre-treatment depend on the application intended for the final product.