Concentration of pineapple juice by osmotic evaporation
Section snippets
introduction
Fruit juice concentration is a fundamental factor for the competitiveness of products and the conquest of new markets as it reduces costs related to operation logistics (packing, storage and transport). The concentration of juices is traditionally accomplished by the use of thermal evaporation. Thermal processes can greatly affect the sensorial and nutritional quality of fruit juices, as these attributes are mainly conferred by heat-sensitive compounds. There is, indeed, a rising demand for
Pineapple juices
A commercial pasteurised, pulpy pineapple juice was used as the raw material. The characteristics of the juice are shown in Table 1. The concentration experiments were carried out with this single strength juice and with the clarified one. For the latter case, the single strength juice was clarified in a micro-filtration system with tubular ceramic membranes of 0.1 μm average pore diameter at 20 ± 1 °C, 2 bar trans-membrane pressure and 6 m s−1 crossflow velocity without enzymatic treatment (
Effect of operating conditions
Some tests were performed before concentrating the pineapple juice in order to evaluate the effect of the temperature difference between both compartments and brine velocity on the evaporation flux. These experiments were carried out with the single strength pineapple juice circulating with a tangential velocity of 1.25 m s−1.
As shown in Table 2, an increase in the temperature of the juice from 20 °C to 35 °C approximately doubled the evaporation flux, whereas the increase in velocity slightly
Conclusion
The concentration of both single strength and clarified pineapple juices using osmotic evaporation achieved TSS contents of at least 56 g 100 g−1. The average evaporation flux was about 6.1 kg h−1 m−2 for the single strength juice and 8.5 kg h−1 m−2 for the clarified juice. The higher flux rate for clarified juice compared with single strength juice indicated some effect of pulp on the evaporation flux. Characterisation of the juice showed no significant changes in the main properties of the pineapple
Acknowledgements
The authors wish to thank CAPES program from the Brazilian Ministry of Education for its financial support and M. Guy SELF (CIRAD, France) for his valuable help in the edition of this article.
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