Influence of Refractance Window evaporation on quality of juices from small fruits

A new type of evaporator (Refractance Window (R) (RW) evaporator) has been developed that operates at atmospheric conditions and uses thermal energy from hot water to concentrate foods. The influence of product temperature and dissolved solids on vitamin C in blueberry juice and color of cranberry juice was evaluated in this new evaporation method in comparison with conventional falling film multi-effect evaporators. During RW evaporation, vitamin C in blueberry juice was reduced by 32% and 48% with product temperatures at 55.5 and 59.0 degrees C, respectively. Concentration of the same juice from single strength to 65 degrees Brix in an industrial failing film evaporator operating at 68 degrees C reduced vitamin C content by 70.1 %. The color of cranberry juice, defined by the hue angle, was not significantly different between the concentrates from the RW and falling film evaporation methods. Further investigation is needed for complete insights into the mechanism for vitamin C loss in RW evaporation. (c) 2006 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.