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