Decolorization of Iranian Date Syrup by Ultrafiltra tion

Abstract

Ultrafiltration (UF) was used for decolorization of an industrial Iranian date syrup. Experimental results were obtained by using two dif ferent 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 tr ans-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 o f 48 and 82%, respectively. When the concentration of date syrup was increased from 40 t o 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 lig htness (L*) and yellowness (b*), while the redness ( a *) was decreased. Changes in the fructose and gluco se levels due to the UF operation were much less than those of color and tu rbidity.