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. Lactose-hydrolyzed milk was also produced by a pure and commercially available beta-galactosidase (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 degrees D, while enhancement of acidity in lactose-hydrolyzed 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 lactose-hydrolyzed milk and ordinary UHT milk (as control) did not show any significant differences with respect to acceptability of sweetness, taste, aftertaste and color.