manufacture of therapeutic yogurt using β-galactosides enzyme extracted from tomato (lycopersicom esculentum l)

the aim of this work was to extract and purify β-galactosidase from tomato (solanum lycopersicum). ten different extraction methods were explored to find the optimal extraction method for the enzyme. the best specific activity of crude enzyme was 212.27 u/mg protein in sodium phosphate buffer (0.1m and ph6). the purifying operations were carried out using 60% ammonium sulfate precipitation. lactase enzyme 600ul/m was used for hydrolyzing lactose of milk. maximum (85–90%) hydrolysis of milk was achieved using a 0.5 percent enzyme concentration at ph 6.5 and incubation at 45 °c for 4 hours. milk whose lactose was hydrolyzed by β-galactosidase was used for the production of stirred flavored yogurt. the sucrose supplied to the products was calculated to compensate the sweetness gained as a result of lactose hydrolysis. the percentages of sucrose saving in stirred flavored yogurt were 4.21, 5.6, 9.4, 11.7, 13.2, 15.3, 18.5 and 21.7 % for lactose hydrolysis percent 23.6, 41.5, 52.2, 6.4, 67.6, 76.6, 83.3 and 87.2%, respectively. the sweetness sensory evaluation of the stirred flavored yogurt showed non-significant differences among hydrolyzed-lactose and the untreated samples.