OSMOTIC CONCENTRATION OF FRUIT SLICES PRIOR TO FREEZE DEHYDRATION

Abstract

Organoleptic quality of freeze-dried foods can be improved by increasing the solids content of the food material to levels of 25–35%. This also results in a reduction of the water load to the freeze-drier, which greatly improves the economics of the process. For solid foods, such as fruit slices, the increase in solids concentration is achievable by an osmosis process. Sucrose has generally been the solute of choice, but economic considerations are indicating that the suitability of new osmosis solutes should be evaluated. Several mixed osmosis solutes were evaluated for their effectiveness in concentrating apple slices prior to freeze-drying. Kinetics of water loss and solute uptake were determined for solutions of differing composition and concentration. Several of the osmotically preconcentrated freeze-dried apple slices were evaluated for organoleptic acceptability.