Effect of temperature and concentration of βeta-galactosidase on the composition of reduced lactose pasteurized goat milk

Abstract This study evaluated the influence of temperature and β-galactosidase concentration on lactose hydrolysis and on the composition of pasteurized goat milk. Goat milk was pasteurized at 75 °C/15 s and cooled to 10 °C and 30 °C, received 0 (control); 0.04%; 0.07%; 0.20% (v/v) β-galactosidase and was incubated for 5 h, followed by enzymatic inactivation at 85 °C. The hydrolysis degree, pH and acidity were evaluated hourly. Physico-chemical parameters were determined after hydrolysis. The maximum hydrolysis degree (100%) has been reached in 4 h when using 0.07% and 0.20% lactase concentrations at 30 °C; however, the minimum hydrolysis percentage of 70% has been reached at 10 °C for all lactase concentrations tested since 1 h of incubation. The degree of hydrolysis and the total acidity of pasteurized goat milk increased with temperature. Low lactase concentrations resulted in an increase in protein levels, total casein, density, total and defatted dry extract. Therefore, combination of low lactase levels and hydrolysis at 10 °C promoted positive changes in lactose-free pasteurized goat milk. This study was the first reporting the changes resulting from enzymatic hydrolysis in the composition of pasteurized goat milk.