The effect of spray-drying and freeze-drying on encapsulation efficiency, in vitro bioaccessibility and oxidative stability of krill oil nanoemulsion system

A nanoemulsion system was employed to encapsulate the krill oil with different concentration. The combination of whey protein concentrate, maltodextrin and gum arabic with the ratio of 8:2:0.5 was used in nanoemulsion formulation to enhance nanoemulsion stability, as well as to construct the wall part of the encapsulates. Two different drying methods; freeze-drying and spray-drying were applied on krill oil nanoemulsion systems to obtained powder encapsulates. The physical characterization of nanoemulsions and chemical stability of krill oil in terms of oxidative stability and in vitro bioaccessibility (%) were evaluated before and after drying processes to understand the effect of different drying techniques on encapsulation ability of nanoemulsion systems. Dehydration of nanoemulsions with spray-drying caused approximately 7 folds increments on particle size. The sample with 8% (w/v) of krill oil concentration had an optimum encapsulation efficiency that was calculated 72% in spray-dried nanoemulsion and 67% in freeze-dried nanoemulsion. Both spray-dried and freeze-dried krill oil nanoemulsions showed similar oxidative stability in 8% (w/v) concentration during the 15 days storage period. In vitro bioaccessibility of encapsulated krill oil was changed between 32.7 to 72.4% and 20.0-83.0% in freeze-dried and spray-dried nanoemulsions, respectively. Still, the spray-drying process is recommended for the dehydration of krill oil nanoemulsion with 8% (w/v) concentration because a better encapsulation efficiency and the higher in vitro bioaccessibility was obtained compared to freeze-dried nanoemulsion systems at the same concentration of krill oil.