There are few reports of purification of plant extracts using ultrafiltration membranes (UF) : The researchers tested different tubular polymer membrane sequences in order to separate the recovered phenols (gallic acid, catechuins, and gallates) from defatted ground grape seeds using acetone-water mixtures based on molecular weight (MW).
The researchers treated water extracts from concentrated press distilled grape dregs through nanofiltration (NF) membranes. The five ceramic NF membranes tested are suitable for concentration purposes. The phenolic content in the retention was increased by three to six times. The researchers propose that the separation of phenolic compounds recovered from distillery sludge can be achieved using three ultrafiltration organic membranes (100 kDa, 20 kDa, 1 kDa). The authors determined that polysulfone membrane can separate phenolic compounds from pectin fractions. They cannot separate different phenols and sugars (reduced or non-reduced) because they are retained in a high percentage even at 100 kDa. In contrast, the application of non-polar fluoropolymer membranes at the UF and NF (1 kDa) boundaries can provide a successful method for separating different phenols. Recently, researchers have proposed a purification method for isolating grapesseed phenol compounds that combines UE (100 kDa) and NF 480 Da) and resin adsorption/desorption.