Concentrating Garcinia mangostana L. rind extract using sequential ultrafiltration and nanofiltration

Mangosteen (Garcinia mangostana L.) rind extract has abundant anthocyanins and phenolic contents which have numerous medicinal properties. It has to be concentrated before being used as additives in food industries. However, the bioactive compounds in the rind extracts are thermolabile and concentration method involved heating is not advisable. Therefore, this study proposes non-thermal sequential ultrafiltration-nanofiltration to concentrate the rind extracts. Polyethersulfone ultrafiltration (PES10) and commercial nanofiltration (NF270) membranes with nominal molecular weight cut-off (MWCO) of 20 kDa and 0.4 kDa were used to concentrate the rind extract obtained from three different solvents, i.e., 10% ethanol, and 10% ethanol acidified with 0.25 M ascorbic acid and citric acid. The filtration process was conducted at transmembrane pressure of 2 and 5 bar, respectively, for 4 h and the changes of density, turbidity, pH, total monomeric anthocyanin (TMA) and total phenolic content (TPC) in the rind extract were recorded. Rejection towards TMA and TPC was above 75% for UF and 86% for NF. Irrespective of the solvents used, density was increased after 4 h of UF and NF, while the pH remains unchanged. Although acidified solvents enhanced the release of anthocyanin and phenolic contents during extraction, but they lowered membrane permeability due to fouling. Rind extracts obtained using acidified solvents had lower concentration efficiency and required higher energy as compared to non-acidified solvents in both UF and NF.

Automated summary

This study investigates the feasibility of non-thermal sequential ultrafiltration-nanofiltration for concentrating mangosteen rind extract. The results show that both ultrafiltration and nanofiltration have high rejection towards total monomeric anthocyanin (TMA) and total phenolic content (TPC), with rates above 75% and 86%, respectively. Acidified solvents enhance the release of anthocyanin and phenolic contents but also result in membrane fouling and lower permeability.