Integrated membrane process for purification and concentration of aqueous Syzygium cumini (L.) seed extract

• Clarification and concentration of S. cumini (L.) seed extract is carried out.
• Integrated membrane process is employed.
• Both purity and antioxidant activity of phenolic extract are enhanced.
• Permeate flux is increased with increasing transmembrane pressure.
• Permeate flux is increased with increasing cross flow velocity (or stirrer speed).

The aim of the present study was to investigate the potentiality of an integrated membrane process for the purification and the concentration of phenolic compounds from aqueous jamun (Syzygium cumini L.) seed extract. The aqueous seed extract obtained at optimal condition (temperature: 49.2 °C, time: 89.4 min, and liquid to solid ratio: 51.6:1 mL/g) was submitted to cross flow ultrafiltration for initial clarification, followed by concentration using nanofiltration under batch concentration mode. A detailed parametric study was carried out to investigate the effect of various process parameters such as transmembrane pressure, cross-flow velocity (or stirrer speed) on the permeate flux and permeate quality. Using classical film theory, a steady state gel polarization model incorporating the effect of transmembrane pressure difference and viscosity variation was proposed for the prediction of permeate flux during cross flow ultrafiltration of aqueous seed extract. The predicted flux values were successfully compared with the experimental results. Experimental results showed that the operating conditions had significant effect on permeate flux, recovery of polyphenols, purity and antioxidant activity of phenolic extract. Ultrafiltration experiments at lower operating pressures (276 and 414 kPa) using 100 kDa membrane resulted in the recovery of 59–66.7% of total polyphenol content in the clarified extract with the purity of 49–58.3% starting from an extract purity of 39.2%. The clarified extract could be successfully concentrated about three times higher using 250 Da nanofiltration membrane at volume concentration ratio of three. The present study revealed that the UF/NF integrated membranes process was successful in clarifying and concentrating phenolic extract obtained from jamun seed with enhanced purity and antioxidant activity.