PERVAPORATION OF A MODEL APPLE JUICE AROMA SOLUTION - COMPARISON OF MEMBRANE PERFORMANCE

The production of concentrated apple juice is associated with major ph ysical and chemical losses of aroma compounds, due mainly to evaporati on, which results in a product with an inferior sensory quality. One m ethod of improving the sensory quality of the juice is to recover the lost aromas by pervaporation and to feed them back to the final produc t. The purpose of this study was to investigate the performance of six different pervaporation membranes for the recovery of apple juice aro mas by pervaporation. As pervaporation of natural apple juice would ca use analytical problems, a model apple juice aroma solution was develo ped, by identification of aroma compounds in apple juice by GC and GC- MS, and used in the experiments. Two polyoctylmethyl siloxane membrane s with different porous support layers and a polydimethyl siloxane mem brane proved to have very good performance, resulting in 100-fold to 1 000-fold enrichment of aromas from the model apple juice aroma solutio n with mass transfer coefficients up to 300 kg/m(2) h. Further investi gations on the long-term effects, the influence of the temperature and the effect of interaction between the membrane and the apple juice, m ust be performed. Economical aspects must also be considered.