Encapsulation of curcumin in CD-MOFs: promoting its incorporation into water-based products and consumption

Curcumin has received considerable interest in functional food areas due to its variety of biological effects. However, its utilization is often limited by its insolubility and instability in aqueous solutions. Herein, curcumin was encapsulated in γ-cyclodextrin metal-organic frameworks (CD-MOFs) to achieve immediate release and rapid dissolution in water just by gentle stirring due to the dissociation of CD-MOFs. The released curcumin exhibited remarkably enhanced stability compared to its free form in aqueous solutions due to the inclusion effects of cyclodextrins. Besides, the impacts of temperature, light and gastrointestinal pH on the chemical stability of curcumin released from basic and neutral CD-MOFs were compared. The molar ratios of curcumin : γ-CD in basic CD-MOFs and neutral CD-MOFs were 1 : 1.7 and 1 : 9.8, respectively. Neutral CD-MOFs were more effective in retarding thermal and gastrointestinal degradation of curcumin because all curcumin molecules can form inclusion complexes with cyclodextrin. Basic CD-MOFs were more conducive to prolonging the half-life time of curcumin during photodegradation since its alkalinity darkened the color of curcumin solution causing lower light transmittance. Moreover, CD-MOFs exhibited higher loading and stability of curcumin due to their unique host-guest structure, than their pure cyclodextrin inclusion complex. Curcumin-loaded CD-MOFs having a fast-dissolving ability accompanied by the improved amorphous form stability of curcumin hold great potential as functional additives in instant food.