Developments in osmotic dehydration of fruits and vegetable-a review

Received: 15/11/2013 Revised: 13/12/2013 Accepted: 16/12/2013 Abstract Osmotic dehydration is a process of water removal by immersion of water containing cellular solids in a concentrated aqueous solution of sugar/ salt. This results in intermediate moisture product with lower water activity. At low water activity, most of the chemical reactions which deteriorate the food as well as the growth and toxins production by microorganisms are ceased. Besides, it improves the color, flavor and texture and is less energy intensive process compared to other drying techniques as no phase change takes place during the moisture removal from the substrate. The product obtained by osmotic process is more stable during storage due to low water activity imparted by water loss and solute gain. Hence, osmotic dehydration is gaining attention in food processing industry as it plays an important role in preservation of perishable foods. It can be applied either as an autonomous process or as a processing step in alternative processing schemes leading to a variety of end products. A lot of research findings are available on the osmotic dehydration of fruits and vegetables. But largescale industrial applications of osmotic processing require a detailed knowledge of different process parameters. This paper presents principles of osmotic dehydration and recent developments regarding the factors affecting osmotic dehydration process i.e. product characteristics, osmotic solution and its composition, product coating, sample to solution ratio, process temperature, process pressure, agitation of osmotic solution and process duration. The details on mathematical modeling of mass transfer during osmotic dehydration of foods, methods to enhance the mass transfer, reuse of the osmotic solution, equipment design for osmotic dehydration are also included as well as the effect of osmotic pre treatment on further processing operations and quality of final product are discussed.