Research On The Inhibition Effect Of Proanthocyandins On The Retrogradation Of Corn Starch

Corn starch is an important composition in starch industry,which plays an important role in the development of national economy.Although corn starch has many advantages in production,such as lower pasting temperature,better rheological and gel properties,corn starch is prone to retrogradation and the stability of freeze-thaw is poor,which is limiting its application in food industry.In order to investigate the effect of proanthocyanidins on corn starch retrogradation,the structural properties,thermal stability,relative crystallinity,viscosity and in vitro digestibility of corn starch samples with different amylose/amylopectin ratios(high-amylose corn starch,common corn starch and high-amylopectin corn starch)with different concentrations of proanthocyanidins were determined.The retrogradation of different corn starch samples was investigated by differential scanning calorimetry(DSC),fourier transform infrared spectrom(FTIR),X-ray diffraction(XRD)and nuclear magnetic resonance spectroscopy(13C-NMR),respectively.For retrogradation of 5 days,the enthalpy of melting decreased with the increasing of proanthocyanidin concentration,which indicated a significant effect of proanthocyanidin on preventing the retrogradation of corn starch.For retrogradation of 10 and 15 days,the enthalpy of melting for high-amylose corn starch showed a minmum value with the concentrations of proanthocyanidin at 2.0%and 2.5%and then increased with adding more proanthocyanidins.For high-amylopectin corn starch,the enthalpy of melting had a low value range from 1.5%?2.0%;while for common corn starch,the enthalpy of melting decreased as the amount of proanthocyanidins increased.XRD results showed that the relative crystallinity of high-amylose corn starch,common corn starch and high-amylopectin corn starch had minmum values of 14.37%,11.83%and 12.10%with the concentrations of proanthocyanidins at 5%,1.5%and 2.5%,respectively.FTIR results indicated that the hydrogen bonding was enhanced by adding proanthocyanidins without the presence of new absorption peak.13C-NMR results suggested that the interaction ways between amylose and proanthocyanidin molecules might be different from that between amylopection and proanthocyanidin molecules.The effect of proanthocyanidins on the viscosity characteristics of corn starch was investigated by the rapid viscosity analyzer.It was found that the addition of proanthocyanidins led to a decrease in the viscosity of high-amylose corn starch samples.The final viscosity of common corn starch was also decreased with the addition of proanthocyanidins,whereas the viscosity of high-amylopectin corn starch increased as the amounts of proanthocyanidins increased.The effect of proanthocyanidins on the in vitro digestion of corn starch samples during the process of retrogradation was also studied.The results showed that the rapidly digested starch of all corn starch samples decreased while the resistant starch increased,suggesting that proanthocyanidins play an inhibitory effect on the enzymatic digestion of corn starch.Scanning electron microscope(SEM)was employed to observe the morphology of corn starch granules during retrogradation.The results showed that the particle surface of retrograded starch granules was no significant change.