Effect of the membrane processing on tannin removal from soluble fraction of Persian gum

Abstract

Tannins, which are known as anti-nutrient compounds with capability of limiting proteins and minerals bioavailability, are present in Persian gum. Ultrafiltration (UF, polysulfone membrane, 30 and 90 kDa, 1, 2 and 5 bar) and nanofiltration (NF, polysulfone, 400 Da, 2.5 and 5 bar) were used to remove tannin from the soluble fraction of Persian gum. The results revealed that the highest amount of tannin removal was achieved in UF (5 bar) and NF (5 bar). However, the use of the membrane process significantly decreased the apparent viscosity of the permeate, which might have an undesirable effect on the functionality of the gum. The effects of membrane molecular weight cut-off, feed temperature, ultrasound pre-treatment, feed concentration and pH, on the amount of tannic acid reduction, and changes in permeate flux, volume concentration factor difference, tannin reduction efficiency, and permeate apparent viscosity were evaluated. The results showed that total tannin removal efficiency was increased by ultrasound pre-treatment, reduction of feed pH, and higher membrane molecular weight cut-off. Increasing the feed temperature and concentration enhanced the apparent viscosity of permeate, although its value was lower than the control sample.