Optimizing process to prepare lactose hydrolysed milk by enzymatic treatment

Lactose intolerance is being reported as a big problem for more than half of the world's adult population. Milk, containing lactose in abundant quantity, is considered as highly nutritious due to its bioactive components while methods are also being explored to use milk with reduced or no lactose content. Aim of this work was to evaluate the influence of process variables viz. enzyme concentration, incubation temperature and incubation time on the percent hydrolysis of lactose in milk, using commercial lactase enzyme so as to produce milk with reduced lactose or devoid of lactose. The conditions for hydrolysis of lactose were optimized using Response Surface Methodology (RSM) by studying the individual and interactive effect of selected variables. At linear level, effect of enzyme concentration and incubation time were found to be highly significant (p<0.01) while at quadratic level, effect of all the three variables were significant (p<0.01) for hydrolysis of lactose in milk. Sweetness of hydrolysed milk was affected by all the three independent variables both at linear and quadratic levels. The optimized process conditions obtained for hydrolysis of lactose in milk include 5152.017 NLU/L of enzyme concentration at 34.4°C for 4.25 hours which resulted in 81.87% lactose hydrolysis and sweetness score of 8.5 for hydrolysed milk.