Production of black-currant juice concentrate by using membrane distillation

In this study the applicability of membrane distillation (MD) was investigated to produce black-currant juice concentrate. For the experiments enzyme treated, pre-filtered by microfiltration and pre-concentrated by reverse osmosis fruit juice was applied. The measurements were carried out in a hollow fibre membrane contactor. Two different temperature differences were investigated as driving force: 15 and 19 °C. The shape of the curves of the fluxes appeared very similar at both temperature differences, however in case of the higher driving force the observed flux was 80% higher than in case of the lower driving force. By the MD process the pre-treated initial juice with 22°Brix total soluble solid (TSS) content was concentrated up to 58.2°Brix.Samples were collected during the concentration process and the density, total acid content (TAC) and anthocyanin content were measured. From the results it can be concluded that all the analysed parameters were directly proportional to the increase of the TSS in the juice. Due to the increase of the TAC the pH of the final concentration decreased under pH = 2.