APPLICATIONS OF ULTRAFILTRATION AND REVERSE OSMOSIS FOR APPLE JUICE CLARIFICATION AND CONCENTRATION (MEMBRANE PROCESSING)

Single strength apple juices, obtained from different stages of a commercial processing line, were clarified and concentrated to 72(DEGREES)Brix by a De Danske Sukkerfabrikker Lab Module 20 plate and frame UF-RO system, and a Niro Atomizer three effect, falling film, pilot evaporator.; Clarification of apple juice by ultrafiltration (UF) using GR-51PP membranes (50,000 molecular weight cut-off, MWCO) at 50(DEGREES)C and 5 bar pressure resulted in an average recovery of 99.6% of the soluble solids, 99.3% of the titratable acids, and up to 41.5% of the enzyme activity. Enzyme recovery decreased as the processing time increased. The sugar composition and flavor quality of the clarified apple juices were not changed by the UF processes. The turbidity of UF clarified juices was less than 0.1 NTU. Cleaning membranes with a 1% Ultrasil solution was more efficient than with a 0.1% NaOH solution. The use of apples from different seasons and storage conditions for juice extraction did not affect the UF processing efficiency.; Concentration of UF clarified apple juice to 20(DEGREES)Brix by reverse osmosis (RO) using HR-95 membranes at 40(DEGREES)C and 40 bar resulted in soluble solids and titratable acids recoveries of greater than 99.7% and 99.5%, respectively. The most energy efficient RO-evaporation (RO-EVAP) process for concentrating single strength apple juice to 72(DEGREES)Brix in the pilot plant involved RO preconcentration to 21(DEGREES)Brix prior to the evaporation.; In the industrial scale RO-EVAP processes using multiple effect evaporators, the energy savings were found increased as the RO preconcentration increased. However, for the evaporation processes using an MVR evaporator, the addition of RO preconcentration may not always save energy. The energy costs between direct evaporation process and RO-EVAP processes were compared using steam/electricity (S/E) cost ratios. An S/E ratio greater than the borderline S/E ratio was considered more economical than the direct evaporation process. A similar method using capital cost ratios between RO systems and evaporators ({dollar}RO/{dollar}EV ratio) was used to estimate the economy of capital investment in an RO-EVAP process. As compared to the direct evaporation process, the RO-EVAP process with actual {dollar}RO/{dollar}EV ratio smaller than the borderline {dollar}RO/{dollar}EV ratio was considered more economical with respect to capital investment.