Freeze-dried capsules prepared from emulsions with encapsulated lactase as a potential delivery system to control lactose hydrolysis in milk

- Spray-dried lactase powder was encapsulated in S/O/W emulsions with 75% efficiency.
- Transglutaminase treatment and caseinate reduced free lactase after freeze-drying.
- Capsules were stable in milk and hydrolyzed lactose by <15% after 3 weeks.
- Capsules reduced the deactivation of lactase during simulated digestions.
- Encapsulation improved the hydrolysis of lactose in milk during in vitro digestions.

The objective of this work was to study solid/oil/water (S/O/W) emulsions as delivery systems with retained lactase in milk and controlled release during in vitro digestion. Spray-dried lactase powder was suspended in anhydrous milk fat/Span® 80 emulsified by sodium caseinate and lecithin (5:1). The S/O/W emulsion had an encapsulation efficiency of 75%, a hydrodynamic diameter of 292 nm, and a zeta potential of −17.37 mV. Cross-linking the dialyzed emulsion with transglutaminase eliminated the detection of free lactase after freeze-drying emulsions and the addition of sodium caseinate further preserved lactase activity. The hydrolysis of lactose in full-fat or skim milk after 3-week storage reduced from >75% for free lactase to <15% for encapsulated lactase. The encapsulated lactase was released gradually during the simulated digestions to hydrolyze lactose in milk more efficiently than free lactase. The present findings suggest S/O/W emulsions are potential delivery systems to incorporate lactase in milk products.