Poly(ethylene glycol) (PEG)-based microgels embedded with magnetic nanoparticles for tannin removal and valorization

Excess tannin in drinks can lead to unpleasant astringent taste, pinking or browning, as well as a decrease in clarity. While protein precipitation method in which various proteins and synthetic polymers are added to induce tannin-protein complexation, followed by separation via sedimentation, is widely used for tannin removal, sedimentation time can take up to few days. In this work, we present poly(ethylene glycol) (PEG)-based microgels embedded with magnetic nanoparticles (MNP) as fining agents for effective adsorption and removal of tannins, using tannic acid (TA) as the model tannin. The PEG microgel with high surface area enables the tannins to effectively adsorb through hydrogen-bonding, and the incorporated MNP enables facile recovery of TA adsorbed microgel via magnetic decantation. We also demonstrate that the PEG microgel is reusable and the TA adsorbed can be also valorized into ellagic acid (EA) by simple base treatment of the TA adsorbed microgels.