The fabrication of yolk immunoglobulin and encapsulation by W1/O/W2 double emulsion.

Yolk immunoglobulin (IgY) has high immune response and potential applications in infection prevention, immune regulation and antibiotic replacement. However, its unstable oral activity and low efficiency of classic extraction process impede IgY application. To shorten the extraction time and maintain relatively high efficiency and activity, we aimed to establish a dilute-freeze-thawing process sequence and a water-in-oil-in-water (W1/O/W2) emulsion to protect IgY against the gastric digestion by encapsulating IgY in the inner aqueous phase. In this work, IgY was extracted with various processing sequence and assessed by macroscopic observation, physicochemical determination and activity measurement. The sequence of dilution followed by freeze-thawing enabled the extraction of relatively higher amounts of IgY while maintaining significantly higher activity. In order to explore its extraction efficiency, the effect of freezing time was explored. Only being frozen for 1 h, IgY extracts had comparable turbidity and chemical composition and even higher activity, which greatly shortened the process compared with previous freeze-thaw-dilution method that needs 8-h freezing. Furthermore, an IgY loading W1/O/W2 double emulsion was fabricated, and physicochemical properties such as morphology and zeta potential, storage stability and microrheology were characterized, and the encapsulation efficiency was approximately 91 %. And the functions of protecting and releasing IgY were estimated through in vitro simulated digestion.