Complexation characteristics between acetylated starch and soy protein isolates and intestinal digestion behavior of the polymers encapsulated active compound

Abstract

The interaction between acetylated starch (AS) and soy protein isolates (SPI) was investigated under different pH conditions, and their corresponding physicochemical properties of the complexes were investigated. This study found that, at pH9.0, the β-turn structure of the protein in the complexes changed into Random coil with the highest ratio, and the thermal stability of the complexes was found to be reduced, which was contributed to the destruction of the crystalline region to a large extent. Meanwhile, the confocal laser scanning microscopy (CLSM) results showed that the complexes demonstrated a dispersed phase at pH5.0, and the SPI structure unfolded maximum at pH9.0. Following the determination of the changes in the rheological property under the existence of NaCl and urea, it was proposed that electrostatic interaction was the major interaction force for all the three complexes. However, hydrophobic and hydrogen bonding forces also seemed to play a more important role for AS/SPI-pH9 complexes than either AS/SPI-pH2 or AS/SPI-pH5 complexes. Complexation significantly increased encapsulation efficiency and loading capacity of curcumin compared to their corresponding individual polymer, followed by a reduced release kinetics at intestinal fluid but not at simulate gastric fluid stage via an in vitro digestion.