Effects Of Pectin With Different Structures On The Physicochemical Properties Of Rice Starch

In this paper,the effects of pectin structure on physicochemical properties of rice starch were investigated.The mathematical model was established between pectin structure parameters and physicochemical properties of starch.In addition,the contribution levels of pectin structure to changes of starch properties were evaluated.Meanwhile,molecular dynamics simulation was used to study the interaction between different structure pectin and starch,and the potential mechanism of pectin structure on starch properties was discussed.The main conclusions of this paper are as follows:Pectin of different structures have different effects on the gelatinization properties of rice starch,and the degree of influence was also different.The mathematical expression between pectin structure parameters and starch gelatinization properties exhibited a good fit,and the relative errors between real value and predicted value of the prediction group were also small.Peak and trough viscosity were mainly affected by DM.The breakdown was positively correlated with GA and negatively correlated with DA.The two main factors which influenced the setback were GA(negative correlation)and MW(positive correlation).The peak time was mainly influenced by DA.The addition of pectin reduced G’ of mixed systems,but the effects on G’’ were varied.The tanδ of the native starch was always the lowest,which indicated the viscosity of the mixed system increased after adding pectin The static shear properties of the native starch and starch-pectin mixed systems have high accuracy of fit to the Power Law model.The fluid index n was less than 1,which indicated that the native starch and starch-pectin mixed systems were typical pseudoplastic fluids and exhibited shear thinning behavior.The shear stability of gel network was improved in the presence of pectin.The effects of pectin on the rice starch retrogradation properties were not consistent,and the effect of pectin on starch in short-term aging and long-term aging were also different.The mathematical model between pectin structure parameters and retrogradation properties performed high accuracy.The relative errors between true value and predicted value of the prediction group was less than or close to 10%,and the aging parameter change of mixed systems can be roughly estimated.The greater the GA,the greater the inhibition of starch retrogradation and the greater impact on short-term aging.The esterification and amide structure of pectin promoted the retrogradation of starch,and the degree of influence increased with the increase of aging time.Molecular weight could promote the short-term aging and inhibit the long-term aging of starch.The potential mechanism of how the pectin structure influence retrogradation properties of the starch is as follows: the presence of pectin molecules in the starch-pectin mixed systems altered the kinetic capacity of the starch molecular segments,which produced different extend of interaction between pectin and starch via the non-bond force,thus,affected the directional migration of starch in the process of aging and the movement space of starch molecular chain.