Characterization and Effects of β–Galactosidase in the Crude Extracts of Cuminum cyminum and Curcuma longa in Preparation of Delactosed Milk and Whey

β-galactosidase (EC 3.2.1.23) was extracted from Cuminum cyminum and Curcuma longa . The crude extracts of these plants were then characterized in term of pH, temperature, and enzyme kinetic. The crude extracts were also used in hydrolysis of lactose in milk and whey. The enzyme activity was measured by its ability to hydrolyze the substrate o-nitrophenyl β -D-galactopyranoside (ONPG). It was found that β-galactosidase in the crude extracts of Cuminum cyminum exhibited maximum activity at pH 8.0 and optimum temperature at 60 °C. While, β-galactosidase in the crude extracts of Curcuma longa have optimum pH at 5.0 and 7.0 and optimum temperature at 50 °C.The K m and V max values of the β-galactosidase in the crude extracts of Cuminum cyminum and Curcuma longa were 4.16 mM and 0.087 μmol/min, and 2.63 mM and 0.333μmol/min, respectively. The results showed that 96.84-97.08% of lactose was hydrolyzed in cow’s milk and whey when treated with crude extracts of Cuminum cyminum and 90-98.6% when treated with crude extracts of Curcuma longa .