Encapsulation of vitamin D in whey protein microgels: stability and foaming properties

Whey protein isolate (WPI) microgels were used as a carrier to effectively encapsulate and protect vitamin D (VD). Cold-set gelation was used to prepare the VD loaded WPI (WPI-VD) microgels, whereby WPI was heat-denatured, cooled, VD was added followed by the addition of calcium chloride (CaCl2) to induce gelation. The WPI-VD microgels were tested for their encapsulation efficiency, stability against temperature (72°C for 15s), UV-light (254 nm), four-week storage (20°C, 4°C and -20°C) and on their foamability. Mechanical whipping was used to prepare the foams which were assessed on overrun and stability. The WPI microgels exhibited high encapsulation efficiency of > 98% and the incorporation of VD did not significantly change the particle size. Moreover, the WPI microgels significantly improved the stability of VD compared to the control (unencapsulated VD) when exposed to environmental conditions. When heated the microgels provided a protective barrier to VD as 97% remained, whereas unencapsulated VD degraded by 25%. UV-light exposure led to complete degradation of VD, however, when encapsulated, 97% VD remained. The microgels could prolong the shelf life of VD as > 92% remained intact at the end of the fourth week compared to ~67% for the control, irrespective of storage temperature. Mechanical whipping of the WPI-VD microgels led to slight degradation of VD. There was no significant difference between the foaming properties of the whipped WPI and WPI-VD microgels as overrun and stability were similar for both samples. This indicated that the addition of VD did not affect the foamability of the microgels. The current work demonstrates that WPI microgels can effectively encapsulate VD, protect against environmental factors while also maintaining the ability to form a stable foam, which has potential applications in food systems.