Effects Of Oat Peptide On The Digestive And Processing Properties Of Potato And Wheat Starches

Starch is an important source of energy for the human body.Natural starch has limitations such as its insolubility in cold water,poor thermal stability and retrogradation,which limit its direct application in food.Combining starch with other ingredients can affect the physicochemical properties of starch,and optimize its application in actual production.Oat peptides are bioactive peptides with Dipeptidyl peptidase IV（DPP4）inhibitory activity obtained through oat proteolysis.Using oat protein and oat peptides as ligands,the complex with potato starch,wheat starch,and waxy corn starch was prepared by hot melt method.The processing properties and interaction mechanism of starch-peptide complexes were analyzed.The main conclusions are as follows:（1）After hydrolyzed by alcalase,the degree of hydrolysis of oat protein was 20.09%.Oat peptides can inhibit the activity of DPP4 in a dose-dependent manner.When the hydrolysis time is120 min,the half-inhibition concentration is 0.49 mg/m L.In the amino acid composition,glutamic acid,arginine,methionine and isoleucine are the most abundant,and contain more hydrophobic amino acids with the total amount reached 57.11%,indicating that oat peptides are very hydrophobic.（2）The addition of oat peptides affected the processing properties of the two kinds of starches.Adding 10%oat peptides increased the resistant starch content of potato starch and wheat starch by 1.77%and 0.83%,and the glycemic index decreased by 2.39 and 1.86,respectively,indicating that it has a certain inhibitory effect on the digestion of the two kinds of starches.For potato starch,10%oat peptide reduced its transmittance by 58.44%and swelling capacity decreased by 6.51%;after being combined with wheat starch,10%oat peptide reduced its water absorption from 134.25%to 123.75%.Generally speaking,although the addition of oat peptides is beneficial to the reduction of starch glycemic index,it has an adverse effect on the processing properties of starch.（3）The mechanism of oat peptides on two kinds of starch was clarified.Rapid Viscosity Analysis（RVA）results showed that oat peptides significantly reduced the viscosity of potato starch,while the breakdown value increased,which is consistent with the previous results of reduced swelling capacity.Differential scanning calorimetry（DSC）results showed that theΔH of potato starch increased from 3.87 J/g to 4.86 J/g after adding 5%oat peptides,indicating that the addition of oat peptides increased the energy required to destroy the starch structure.In the Fourier transform infrared spectrum（FTIR）,the absorption peak at 3410 cm^-1 of potato starch moved towards the direction with a large wave number,and the absorption peak became sharp,indicating that the free hydroxyl group increased,and a certain concentration of oat peptides could inhibit the formation of hydrogen bonds between starch molecules.X-ray diffraction（XRD）results showed that the addition of oat peptides can reduce the crystallinity of potato starch and inhibit the starch retrogradation.The above results indicated that oat peptides are mainly combined with starch through hydrophobic interactions,inhibiting changes in the binding capacity and structure of starch and water molecules,and affecting the processing properties of starch.Oat peptides can effectively inhibit the gelatinization and digestion of potato starch,but the effect on wheat starch is not significant.This provided a reference for oat peptides added to different types of starch to develop new functional foods.