decolorization of iranian date syrup by ultrafiltration

ultrafiltration (uf) was used for decolorization of an industrial iranian date syrup. experimental results were obtained by using two different concentrations of the date syrup (40 and 50 °brix) and two different membrane pore sizes (15-20 and 30-50 kda molecular weight cut-off values) under different trans-membrane pressures (tmp: 40, 70, 110 and 150 psi). the membrane with a pore size of 15-20 kda resulted in average decolorization of 56% and turbidity reduction of 90%. increasing tmp from 40 to 150 psi led to the decolorization and turbidity reduction of 48 and 82%, respectively. when the concentration of date syrup was increased from 40 to 50 °brix, the levels of decolorization and turbidity reductions reached 47 and 78%, respectively. reduction in the turbidity of date syrup was correlated with increases in the lightness (l*) and yellowness (b*), while the redness (a*) was decreased. changes in the fructose and glucose levels due to the uf operation were much less than those of color and turbidity.