The process of lactose hydrolysis is simple and does not require special equipment in dairy plants. When using a single-use enzyme for lactose hydrolysis, several factors must be considered. These include substrate concentration, pH of operation, maximum temperature and contact time permissible, enzyme activity and cost. An extensive contact time at 35-
45 maybe required to reduce costs, but with milk this usually results in extensive microbial growth. Alternatively, overnight holding at refrigeration temperature may be employed . Soluble lactases used are generally of microbial origin