Athermal concentration of apple juice by forward osmosis: Process performance and membrane fouling propensity

Abstract

The athermal concentration as green and sustainable technique is desired for fruit juice concentration to improve product quality and decrease the energy consumption. The emerging forward osmosis (FO) process was employed for apple juice concentration at ambient operational conditions in order to preserve juice nutrition and flavor. The parameters of FO process (membrane property, crossflow velocity of feed solution (FS), type of draw solutes, and concentration of draw solution (DS)) were detailedly investigated for the effects on water flux, membrane fouling control and membrane cleaning. The content of total soluble solids (TSS) in the apple juice was increased from 11°Brix to 60°Brix. The acidity and total phenols were both increased by 4.07-fold and 4.92-fold, respectively. The apple juice can be concentrated up to about 5.45-fold according to TSS by a single stage FO process after 48 h. The membrane fouling mechanism was investigated by the flux change with and without the pectin. Furthermore, different methods of membrane cleaning were further assessed to recover the water flux. Hydraulic flushing could efficiently recover the flux up to 95.2%. The optimization of the FO process parameters could further facilitate FO process for athermal concentration of apple juice, which may have great potentials for the practical applications in the food processing.