| The main objective of this research was to investigate the potential application of pervaporation to the manufacture of grape juice essence and the extraction of diacetyl from aqueous solutions. The main findings of this study were: (1) It is indeed possible to manufacture grape juice essence by pervaporation. Starting with a 150x fold essence, it was possible to produce essences that were rated a 1000x fold by industry. (2) Model solutions of methyl anthranilate in water and essence solutions behaved similarly with respect to fluxes and enrichment factor. This suggests that even though essences are multicomponent solutions, the low concentrations in which the components are present preclude any multicomponent interaction. Thus, it is possible to work with simple solutions and obtain data that can be used for scaling up. (3) The irreversible thermodynamics model was extended to explain the transport of high boilers like methyl anthranilate. (4) Most of the work was done with PDMS-PC membranes that were relatively thick (1 mil). This resulted in lower fluxes. However, even if one were to use much thinner membranes and expect a proportional increase in fluxes, it may still be not economical to practice direct aroma extraction of juice. Membranes like PEBAX, exhibit higher selectivity and flux and need to be investigated more actively. At present, we feel that the concentration of commercial essences is practical. (5) The extraction of diacetyl from aqueous solutions and whey permeate was shown to be feasible. We feel this process is practical even with currently available membranes. The transport behavior of diacetyl and water could be modelled simply without any interaction effects. |
