Encapsulation of betalain into w/o/w double emulsion and release during in vitro intestinal lipid digestion

- Betalain encapsulated in the inner water phase of a w/o/w double emulsion.
- Effect of in vitro lipid digestion on emulsion structure and betalain release studied.
- Aggregation of w/o/w droplets and coalescence of w/o droplets during in vitro digestion.
- 35% release of betalain during in vitro intestinal lipid digestion.

A water-in-oil-in-water (w/o/w) double emulsion was prepared with water extract of red beet as the inner water phase, rapeseed oil as the oil phase and polysaccharides solution as the outer water phase. Polyglycerol polyricinoleate and polar lipid fraction from oat were used as emulsifiers for primary water-in-oil (w/o) emulsion and secondary w/o/w emulsion, respectively. Their mean droplet sizes were approximately 0.34 μm and 5.5 μm, respectively. The double emulsion showed a high encapsulation efficiency of 89.1% and had a pink coloration due to encapsulated betalain. The double emulsion was subjected to in vitro intestinal lipid digestion and the evolution of structures and release of betalain were monitored. During the first 2 h of digestion, coalescence of the inner water phase droplets was observed, and the sizes of the double emulsion droplets increased quickly because of aggregation. This period also corresponded to release of betalain, reaching about 35%. After 3 h of digestion, no more release was measured, corresponding to no further increase in droplet sizes. In contrast, the encapsulation efficiency and droplet sizes were not affected after 3 h in the same digestion conditions but without the bile salts and lipase, showing they were responsible for the release.