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 (۴۰ and ۵۰ °Brix) and two different membrane pore sizes (۱۵-۲۰ and ۳۰-۵۰ kDa molecular weight cut-off values) under different trans-membrane pressures (TMP: ۴۰, ۷۰, ۱۱۰ and ۱۵۰ psi). The membrane with a pore size of ۱۵-۲۰ kDa resulted in average decolorization of ۵۶% and turbidity reduction of ۹۰%. Increasing TMP from ۴۰ to ۱۵۰ psi led to the decolorization and turbidity reduction of ۴۸ and ۸۲%, respectively. When the concentration of date syrup was increased from ۴۰ to ۵۰ °Brix, the levels of decolorization and turbidity reductions reached ۴۷ and ۷۸%, 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.