Interactions between caffeic acid and corn starch with varying amylose content and their effects on starch digestion

This study aimed to evaluate the physical-chemical interaction between caffeic acid (CA) and gelatinized corn starch with varying amylose and its potential effect on starch digestion. Iodine binding reaction indicated that the absorbance of starch-iodine complex was lower than that in the starch-CA sample. Furthermore, the decrease of absorbance in high amylose corn starch was the most obvious. The affinity constant for CA obtained by isothermal titration calorimetry analysis increased with the amylose content. In the 1H NMR analysis, the peaks of starch hydroxyl groups at 5.4 and 5.5 ppm became broader after the addition of CA, demonstrating that CA interacted with the selected starches via the hydroxyl groups to form hydrogen bonds. In vitro digestibility studies revealed that the interaction between CA and starch had different effects on starch with different amylose content. Moreover, it was revealed that 2% of CA promoted the hydrolytic process, but a drastic reduction of the hydrolytic process occurred upon increasing the CA to 10% for CS. These results suggested that amylose content and certain interactions with CA was a potential reason affecting the mode of interaction, thus altering the digestion.