Physicochemical and sensory properties of milk supplemented with lactase microcapsules coated with enteric coating materials

In this paper, we report the physicochemical and sensory properties of milk supplemented with a powder of microencapsulated lactase. The core material was lactase (beta-galactosidase), the primary coating material was medium-chain triglyceride (MCT), and the secondary (enteric) coating material was either hydroxypropyl methylcellulose phthalate (HPMCP) or shellac, comparing both against market milk as a control. The physicochemical properties of both types of microcapsules were analyzed, including the particle size, zeta potential, and in vitro release behavior. To survey the stability of the microcapsules in milk during storage, we studied the residual lactose content and pH. Furthermore, to determine the properties of milk supplemented with the microcapsules, changes in color and sensory properties were evaluated during storage. The particle sizes (volume-weighted mean; D[4,3]) of the microcapsules coated with HPMCP or shellac were 2,836 and 7,834 nm, respectively, and the zeta potential of the capsules coated with shellac was higher than the zeta potential of those coated with HPMCP. The pH levels of milk supplemented with the lactase microcapsules were similar to those of the control (unsupplemented market milk); however, for milk supplemented with HPMCPcoated microcapsules, the pH was slightly lower. The core material, lactase, was released from the microcapsules during 12-d storage, and 18.82 and 35.09% of lactose was hydrolyzed in the samples for HPMCP-and shellac-coated microcapsules, respectively. The sensory characteristics of milk containing microcapsules coated with HPMCP did not show significant differences from the control, in terms of sweetness or off-taste, until 8 d of storage. However, shellac-coated microcapsules showed significant difference in sweetness and off-taste at d 8 and 6 of storage, respectively. The color of milk containing HPMCP-coated microcapsules did not show a significant difference during storage. However, that containing shellac-coated microcapsules was somewhat higher in color values than others. In particular, it showed significance from 0 to 4 d storage in L* and C* values. In conclusion, a powder of lactase microcapsules coated with HPMCP can be suitable as a supplement for milk.