ABSTRACT
Osmotic dehydration is a gentle way of removing water from plant tissues such as fruits or vegetables. The fruit pieces are very soft and still subject to spoilage by a variety of microorganisms. The water content needs to be lowered further to gain microbiological stability without cool storage. The chapter utilizes microwave-vacuum dehydration to achieve shelf stability. In osmotic dehydration, pieces of fruit or vegetable are immersed in an aqueous solution. Sucrose or mixtures of sugars are normally used for fruits. The applicaton of an osmotic treatment before microwave-vacuum drying combines some advantages of both unit operations. When untreated pieces of apple or strawberry are microwave-vacuum dried, they will normally shrink, sometimes as much as air-dried samples. Osmotic pretreatments provide a tool for incorporating sucrose in the food, which may already contain pectins. Fresh apple and strawberry pieces needed longer microwave drying.
