in-house production of lactose-hydrolysed milk by beta-galactosidase from lactobacillus bulgaricus

crude enzyme (beta-galactosidase) extract (cee) was produced by lactobacillus ssp. bulgaricus chr hansen lb-12 and was applied in sterile milk which had been processed through ultra high temperature method (uht milk), for hydrolyzing lactose. lactosehydrolyzed milk was also produced by a pure and commercially available betagalactosidase (maxilact). optimum quantities of cee and maxilact enzyme, for producing lactose-hydrolyzed milk, during 6 hours of processing, were 0.418 and 0.512 u ml-1, respectively. using more than 0.418 u ml-1 cee resulted in unacceptable acidity. acidity of lactose-hydrolyzed milk produced through 0.418 u ml-1 of cee was significantly increased from 15 to 17 ºd, while enhancement of acidity in lactosehydrolyzed milk produced through maxilact enzyme was not significant. total count of lactose-hydrolyzed milk by 0.418 u ml-1 cee, after 6 hours of processing was significantly increased from 5 to 30 cfu (colony forming unit). sensory evaluation of lactosehydrolyzed milk and ordinary uht milk (as control) did not show any significant differences with respect to acceptability of sweetness, taste, aftertaste and color.