Microwave vacuum drying in the food processing industry

Abstract

Heating and drying of food by microwaves is a well established technology, and it is well known, that the combined application of microwave energy and vacuum creates food products with properties comparable to freeze drying, e.g. in terms of instant properties, but in shorter time and thus, at lower costs. Developmental work was done at Battelle Ingenieurtechnik with the objective, to use this technology not only for the processing of pasty and liquid products, but also for bulk products and to establish it on an industrial scale. It resulted in a successful industrial application for the production of vegetables as ingredients for instant" soups and sauces, of crispy and crunchy fruits as ingredients for e.g. muesli, yoghurt etc. and entirely new products like e.g. fruit snacks, vegetable snacks or other kinds of snacks. The development was started after an extensive market analysis which revealed the demand for the products as mentioned above. The development includes simulations in order to maximize power density and, at the same time, to avoid plasma discharges in the vacuum cavity. A laboratory plant and, finally, a full scale unit was designed and constructed, which successfully went into operation. In the meantime, four more stations of the same size, including additional equipment like pre-dryer, post-dryer and some preparation components have been installed for the processing of vegetables, fruits and berries. This paper describes, how our microwave vacuum dryer had been developed and which results were obtained. A perspective on further development is given as well. © Springer-Verlag Berlin Heidelberg 2006.