Effects of Sub-gelatinization Heat Treatment on Functional Properties of Corn Starch-Piperine Complex

In order to explore the effect of piperine-corn starch complex on its structure and physicochemical properties at sub-gelatinization temperature, corn starch was used in this study to prepare sub-gelatinized corn starch-piperine complexes at 60 °C. Gelatinization viscometer, differential scanning calorimetry, fourier transform infrared spectroscopy and X-ray diffraction were used to characterize the complex. The results showed that piperine was successfully loaded on the sub-gelatinized corn starch with the loading rate of 39.45%. The scanning electron microscope results showed that piperine was successfully loaded in the swelled cracks of starch granules. The particle size increased from 15.20 μm (natural corn starch) to 25.80 μm (sub-gelatinized corn starch) and 81.90 μm (sub-gelatinized corn starch-piperine complex). The addition of piperine reduced the peak viscosity and trough viscosity of the sub-gelatinized corn starch. No new group or chemical bond was observed in the infrared spectrum of the complex while the addition of piperine enhanced the intramolecular and intermolecular hydrogen bonding between corn starch and piperine. X-ray diffraction showed that the relative crystallinity was increased from 23.52% (native corn starch) to 28.15% (sub-gelatinized corn starch-piperine complex) while the crystalline structure of the corn starch was not changed during the sub-gelatinized treatment. Compared to the native corn starch, the gelatinization enthalpy of the sub-gelatinized corn starch and the sub-gelatinized corn starch-piperine complex significantly decreased. The addition of piperine showed little effect on the structure of the sub-gelatinized corn starch, but it showed a significant impact on its physicochemical properties. This study would provide an important basis for the interaction and complex mechanism between starch and piperine.