Thermoelectricity applied to the cryoconcentration of orange juice

Abstract

The high content of water in natural fruit juices suggests the reduction of their volume by its elimination. This is a concentration process for juices that saves space and reduces costs for storage, transport and handling. This paper describes the main features of a prototype of a "cryoconcentration cell" for obtaining concentrated orange juice. This development is being supported by a research project within the program of the CICYT, a Spanish Government Agency to promote R&D activities. The prototype proposes the use of the Peltier effect as an alternative to the traditional methods of cryoconcentration using the aforementioned conventional techniques. The cryoconcentration cell uses a set of thermoelectric elements to produce the cooling conditions able to convert the excess of water included in the juice into ice so that later it is possible to eliminate it and to concentrate the juice. The orange juice is the hot sink in our application. The heat extracted from the orange juice is transferred to water in circulation, which is the cool sink. A first prototype of this cell was constructed in aluminium. From this experience another prototype was constructed in copper which is an improvement over the first one. Both prototypes of cryoconcentration cells use 16 thermoelectric elements on both main sides of the recipient that temporarily contains the juice. A detailed description of the last prototype, its design and some initial results obtained are presented in this paper.