Concentration of Red Clover Juice using Reverse Osmosis and Membrane Distillation

The juice from red clover (Trifolium pretense L.) has a high content of isoflavones. Especially red clover contains four important isoflavones with estrogenic activity: genistein, daidzein, and their methyl ether derivatives, biochanin A and formononetin which show beneficial effects on menopausal women. The present study investigated the use of an integrated membrane process to concentrate a fermented red clover juice sold as a herbal juice beneficial for menopausal women. The main motivation is the reduction of storage volume and potential pharmaceutical applications of the concentrate, while at the same time retaining the original content of active compounds and dissolved solids.
The juice was first pre-filtered through a stainless steel sieve to remove larger solids and then clarified by microfiltration (MF). The clarified permeate from the MF was concentrated by reverse osmosis (RO). The total solid (TS) content of the MF permeate was 4.3 % (w/w) while the RO-retentate reached a TS of 9.98 % (w/w). The RO-retentate was then subjected to direct contact membrane distillation (DCMD) to obtain a final juice concentrate of up to 30.7%(w/w) of TS content. The RO and DCMD processes showed total retention of the isoflavonoids. Therefore, the integrated membrane process allowed the concentration of a fermented red clover juice at low temperatures without thermal damage of the compounds of interest.
For some natural medicine applications only removal water is allowed. If the juice was reconstituted by mixing the DCMD concentrate with the solids retained on the metal sieves and the retentate fraction from the, the concentrated juice had a 2 times higher TS, and a isoflavonoid content that was 1.5 times than in the fermented juice fed to the process.