Preparation of lactose-free milk by using salt-fractionated almond (Amygdalus communis) β-galactosidase



β-galactosidase was isolated from almond (Amygdalus communis) extract by ammonium sulfate precipitation. Almond proteins precipitated by using ammonium sulfate and then dialysed exhibited 5.3-fold purification of β-galactosidase, and the yield of enzyme preparation was 96.5%. The partially purified β-galactosidase exhibited pH and temperature optima at pH 5.5 and 50 °C, respectively. The enzyme was significantly stable against heat, pH, calcium and magnesium ions and D-galactose. The almond β-galactosidase preparation exhibited over 89% activity even after 2 months storage at 4 °C. Hydrolysis of lactose in milk and whey was performed in a stirred batch process by using this enzyme preparation. These observations indicated that the hydrolysis of lactose increased continuously with time. The enzyme could hydrolyse 94% of lactose in buffer solution and whey whereas 90% of lactose hydrolysis was achieved in milk. The main aim of the present study was to prepare lactose-free milk, which must be free from contamination, and the process should be inexpensive. Copyright © 2007 Society of Chemical Industry