Production of low-dosage lactose milk using lactase immobilised in hydrogel

A hydrogel based on chitosan was employed for the immobilisation of lactase with the aim of hydrolysing lactose and producing low-dosage lactose milk. The degree of swelling of the hydrogel was affected by the type of aqueous solution, pH and temperature. The lactase immobilisation capacities at pH 4.0 and pH 7.0 were 257.12 ± 3.18 and 157.87 ± 1.96 mg enzyme per g dried hydrogel, respectively, after 1440 min at room temperature. The activity of immobilised lactase ranged from 97.91 to 56.04 and 97.91 to 71.80% from the first to the tenth cycle of hydrolysis of standard lactose and lactose contained in UHT milk, respectively. Immobilised lactase in hydrogel could be applied for the production of low-dosage lactose milk for at least ten successive hydrolysis cycles. Moreover, hydrogels containing immobilised lactase could also be useful for the enzyme release in individuals with lactose intolerance.