The Effect Of Tea Polyphenols On The Structure And Physicochemical Properties Of Rice Starch

Small molecular substances interact with starch to affect the gelatinization process of starch and changed the properties of products during the production.In recent years,tea polyphenols(TP)as a natural small molecular substance,the interaction between TP and starch has been widely concerned.In this paper,the effects of TP on the structure and physicochemical properties of rice starch(RS)were studied from the aspects of thermal properties,particle morphology,aggregation morphology and crystal structure by two different methods of conduction heating(CH)and high hydrostatic pressure(HHP).The results were used to elucidate the interaction between TP and RS.It was significance to regulate the processing of starch products by TP and other small molecular substances.The main conclusions were as follows:(1)The effect of TP on gelatinization of RS under conduction heating was studied.The results of differential scanning calorimetry(DSC)showed that TP reduced the gelatinization temperature and enthalpy of rice starch under conduction heating.Combined with the results of DSC,the effects of TP on the granule structure,swelling ratio and solubility,viscosity characteristic value and water distribution of RS were monitored.The results showed that TP affected the changes of RS granule structure and the distribution of water migration during gelatinization,destroyed the movement state of granule structure and molecular chain of RS at low temperature.TP promoted the water absorption and swelling of RS at low temperature.The gelatinization temperature of RS was reduced by TP under conduction heating.(2)The results of UV and 1H-NMR showed that the interaction between TP and RS hindered the space of starch and iodine to form copolymer,which reduced the absorbance of starch iodine complex,and affected the peak splitting of TP under the external magnetic field.In order to further clarify the interaction between TP and RS molecules.It was observed by AFM that TP blocked the spiral formation of RS molecular chain and caused the deformation of RS condensed state.The results of dielectric spectroscopy showed that the RS/TP system produced dipole polarization,which promoted the fracture of RS molecular chain and enhanced the movement of starch molecular chain during the heating process.(3)Effects of TP on the multi-layer structure and physical and chemical properties of RS gelatinization induced by HHP at room temperature.Differential scanning calorimetry(DSC)showed that there was no significant effect of TP on the gelatinization of RS below 400 MPa treatment.The gelatinization degree of RS in a dose-dependent with TP under 400 MPa.When the TP solution contacted with starch granules and formed a very thin adhesion layer,which attracted by both water molecules and starch granules.There was a concentration difference of TP,internal and external of RS granules.TP permeated into RS granules by HHP,which destroyed the internal structure of starch granules and promoted water to enter the amorphous region.At the same time,the crystal structure connected with it was destroyed by water swelling.From the structure of starch granules,with the increasing of the TP,the polarization cross of RS gradually disappeared and the gel structure appeared.In terms of intermolecular interaction,TP occupied the hydrogen bond binding sites of RS molecules,changed the intermolecular and intramolecular hydrogen bond binding of RS,and changed the proportion of crystalline and amorphous areas of RS.In terms of crystal structure,TP promoted the transformation of RS from A-type structure to B+V-type structure,and the crystallinity decreased.From short-range ordered structure,TP not only affected the hydrogen bond between RS molecules,but also changed the irregular state of starch molecules in the amorphous region.(4)TP infiltrated into the starch granules under 400 MPa,the long amylose molecular chain broke into more short amylopectin.The friction coefficient reduced and changed the viscosity parameters of RS.TP also weakened the gel strength of starch paste,indicating that the RS/TP system showed greater shear thinning behavior.At the same time,the solubility and swelling rate of RS increased significantly with the increase of TP at low temperature(40-60?).TP further enhanced the disorder of RS molecular chain arrangement.There was more conducive for RS to adsorb water molecules,and enhanced the flow of water molecules between RS molecular chains.