Preparation, physicochemical characterization and in vitro digestibility on solid complex of maize starches with quercetin

The objective of this study was to prepare and characterize solid complex of starch with quercetin. Starches with different content of quercetin were prepared and their formation was confirmed by the presence of the carbonyl signal around 1662 cm⁻¹ in the FT-IR spectra. Scanning electron microscopy (SEM) suggested most of the starch granules disintegrated with many visible fragments along with increasing quercetin content in the binary mixtures. X-ray diffraction (XRD) of quercetin-starch complexes revealed that the crystal structure of native starch was disappeared and new crystalline regions were formed. The thermal behavior of quercetin-starch was investigated using thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC). It was observed that the mass loss and thermal stability of complexes depend on the content of quercetin in the complexes. There were obvious differences between pregelatinized starch and quercetin-starch complexes in digestion rate. The digestion rate was drastically reduced as the quercetin was blended. The digestion rate was steady at about 37.3% for pregelatinized starch and 10.1% for quercetin-starch complex (2.5 g/100 g) after incubating 2 h. The residual starch of quercetin-starch complexes can be thought as resistant starch, the amounts of resistant starch were sharply increased in comparison with the pregelatinized starch.