Solubility, stability, and bioaccessibility improvement of curcumin encapsulated using 4-α-glucanotransferase-modified rice starch with reversible pH-induced aggregation property

Abstract

Curcumin is a polyphenolic compound with anti-cancer, anti-inflammatory and anti-oxidant effects. However, its application in the food industry is very limited owing to its low water solubility and chemical stability. In the present study, 4αGTase-treated rice starch (GS) was prepared by treating rice starch with 4-α-glucanotransferase (4αGTase) for 1 h (1 GS) and 96 h (96 GS), and the physicochemical properties of GS were analyzed. Moreover, the capability of GS to improve the encapsulation efficiency and stability of curcumin by forming complexes was investigated in comparison with maltodextrin (MD) and β-cyclodextrin (CD). GS is known to contain cyclic glucans and amylopectin clusters that contribute to its complex forming capability with bioactive compounds. Upon encapsulation with 1 GS and 96 GS, curcumin solubility increased by 2,241- and 2,846-fold, respectively. UV stability of the encapsulated curcumin with 96 GS also improved by 1.83-fold. GS was effective under all pH conditions except for 96 GS under acidic condition, as well as curcumin encapsulated with 1 GS and 96 GS exhibited 11.53- and 11.27-fold increase in bioaccessibility. The increased stability of curcumin within GS may be attributed to the unique molecular structure of GS interacting with curcumin, as suggested by chromatography and Fourier transform infrared spectroscopy. Also, the improved bioaccessibility of curcumin encapsulated with 96 GS even with lower pH stability at acidic pH seems to be partly attributed to reversible pH-induced aggregation of 96 GS. These results suggest that GS could act as a novel food-grade host material to improve the chemical stability of curcumin.