Spray-drying microencapsulation of curcumin nanocomplexes with soy protein isolate: Encapsulation, water dispersion, bioaccessibility and bioactivities of curcumin

The spray-drying microencapsulation of curcumin encapsulated in soy protein isolate (SPI) nanocomplexes, as well as the influence of spray-drying on encapsulation, water redispersion behavior, bioaccessibility, and bioactivities (antioxidant and anti-cancer) of encapsulated curcumin, was investigated. The addition of soy soluble polysaccharide (SSPS) and/or maltodextrin (MD), alone or in a combination, prior to the spray-drying, greatly improved the microencapsulation performance of the nanocomplex, and water dispersion behavior of the corresponding spray-dried powders. Regardless of the addition of SSPS or MD, the spray-drying remarkably decreased the bioaccessibility of encapsulated curcumin, which seemed to be associated with the aggregation of the nanocomplexes. The curcumin encapsulated in the spray-dried nanocomplex exhibited a much higher oxygen radical absorbance capacity than free curcumin (in DMSO). Both free and encapsulated curcumin showed a remarkable cytotoxicity or anti-proliferation against human hepatal carcinoma HepG2 cells, but the effects were highly dose-dependent. In the cytotoxicity evaluation, at high curcumin concentrations, e.g., 40–80 μM, encapsulated curcumin induced apoptosis of the cells, to a significantly less extent, than free curcumin. However, in the anti-proliferation case, at low concentrations (e.g., <30 μM) the encapsulated curcumin exhibited a more effective inhibition of cell proliferation than free curcumin. At high concentrations (>30 μM), both free and encapsulated curcumin inhibited the cell proliferation via the arrest of cells in G2/M phase, while at low curcumin concentrations, the antioxidant activity might largely account for the inhibition effects. The findings would be of importance for the use of soy protein nanocarriers for encapsulation and delivery of poorly soluble bioactives, in the functional food formulations.