Synergistic Effect Of Lotus Seed Starch Blended With Different Hydrocolloids And Its Mechanism

Starch is one of the main components of lotus seed,which is a specific starch with high amylose content.In the processing of lotus seed juices and other products,lotus seed starch?LS?is prone to recrystallization,causing the quality deterioration of such products in the processing and storage,restricting the development of lotus seed products,and for expanding the functional characteristics of LS.The hydrocolloids?chitosan,CS;guar gum,GG;xanthan gum,XN?was used to modify lotus seed starch?LS?in this paper,the synergistic effect of LS and hydrocolloids on anti-retrogradation and slowly digestion were studied systematically from rheology,interaction force,retrogradation and digestibility,the involved mechanism was revealed.Based on the rheological properties and molecular dynamics simulations technology,the interaction between LS and hydrocolloids was discussed.The effect of hydrocolloids on the short-term and long-term retrogradation of LS and its mechanism were explored.Based on that,The effect of hydrocolloids on the stability of lotus seed emulsion was revealed,the digestibility of LS-CS blends were analyzed to clarify their synergistic effect on slowly digestion.The results could provide the important theoretical value and practical significance for expanding LS function and regulating the anti-retrogradation ability of lotus seed juice and other products.?1?Study on the interaction between lotus seed starch and hydrocolloidsThe rheological properties of LS and LS-hydrocolloid blends were studied after autoclaving treatment,the interactions between LS and hydrocolloids were explored by rheology and molecular dynamics simulations technology.The results showed that the different hydrocolloid and LS could play a synergistic role in thickening,and the apparent viscosity,shear stress,elastic modulus as well as viscous modulus of LS blends were increased significantly hydrocolloids.The addition of CS caused an increase in fluid index n and a decrease in damping factor tan?of LS,suggesting LS-CS blends were more like-solid gel than LS alone,which was related to the enhancement of molecular interaction by the phase separation.The main molecular forces of LS-CS blends were hydrogen bonding and electrostatic interaction,while hydrogen bonding was the main force of LS-GG and LS-XN blends.Molecular dynamics simulations analysis exhibited that CS enhanced the non-covalent bonding and the ordered structure of LS.However,XN and GG weakened the non-covalent bonding of LS and hindered the ordering degree of the system,suggesting that different hydrocolloids could affect the retrogradation behavior of LS.The difference of molecular forces between LS and hydrocolloid could provide the theoretical basis for the subsequent research on the effect of hydrocolloids on the retrogradation of LS.?2?Study on the short-term retrogradation of lotus seed starch-hydrocolloid blendsThe short-term retrogradation behavior and molecular structure of LS and LS-hydrocolloid blends were studied,to discusse the mechanism of hydrocolloids affecting the short-term retrogradation of LS.The results showed that the storage modulus G'value of LS-CS blends increased much fast than LS alone,exhibited greater synersis,suggesting CS could increase the short-term retrogradation of LS.It might be due to the increased ordered structures,the decreased average molecular weight?M_w?and the greater leaching amylose content in the LS-CS blends.LS-GG,especially LS-XN blends displayed the opposite trends,indicating GG and XN could delay the short-term retrogradation of LS.Coating effect of GG or XN on LS was observed by laser confocal scanning microscope,which could inhibit the granules swelling and amylose leaching,thus to delay starch retrogradation.The difference of molecular force in various LS-hydrocolloid blends affected the granule swelling and the content of amylose leaching in the LS system,altering the ordered structure degree.In conclusion,CS could promote the short-term retrogradation of LS,while GG and XN can inhibit that,and the inhibition effect of XN is better,which is related to the molecular force between LS and hydrocolloid blends.?3?Study on the long-term retrogradation of lotus seed starch and hydrocolloid blendsShort-term retrogradation is related to recrystallization of amylose,while amylopectin dominates the long-term retrogradation of amylose,and the effect is more complex than that of amylose.Therefore,in order to further study the effects of hydrocolloids on the long-term retrogradation of LS,the water distribution,migration,molecular structure and textural properties of LS and LS-hydrocolloid blends were analyzed.The results showed that LS contained bound water(T₂₁),immobilized water(T₂₂),less mobility free water(T₂₃)and higher mobility free water(T₂₄).CS increased the content of higher mobility free water(A₂₄)in LS,GG increased the content of bound water(A₂₁),and XN increased the content of less mobility free water(A₂₃)in LS,indicating that different hydrocolloid caused different water distribution of LS.Compared with LS alone,CS increased the water migration of LS,and the water molecules were easy to diffuse as T₂₄.GG and XN would interfere the water migration and synersis.The results of X-ray diffraction,infrared spectroscopy and laser Raman imaging showed that the content of the ordered structure of LS was increased by CS at the early stage of cooling storage?<7 d?,while it was significantly decreased at the late stage of cooling storage.While the content of the ordered structure of LS was decreased by GG and XN.Texture analysis showed that CS increased the hardness of LS gel at the early stage of cooling storage,but resulted in a decrease on that at the late stage of cooling storage,meanwhile its springiness value was lower than that of LS alone.GG and XN reduces the hardness of LS and improves its springiness,but the effect of XN were decreased in the late cooling storage.The results showed that XN could effectively inhibit the short-term retrogradation of LS,which was related to the inhibition of recrystallization of amylose;while GG could effectively inhibit the long-term retrogradation of lotus seed starch,which was related to the inhibition of recrystallization of amylopectin.The results provide a theoretical basis for the improvement of anti-retrogradation ability and the extension of shelf life of starchy products such as lotus seed juice.?4?Study on the effect of hydrocolloids on the stability of lotus seed emulsionOn the basis of the effects of hydrocolloids on the short-term and long-term retrogradation of LS,the effect of hydrocolloids on the stability of lotus seed emulsion was studied.The partical size distribution,stability and the amount of starch precipitation in lotus seed emulsion with different hydrocolloids systems were investigated during cold storage.The results showed that GG could significantly improve the granules'homogeneity and stability of lotus seed emulsion,delaying the phenomenon of agglomeration and starch precipitation,while CS caused the aggregation of large starch granules and poor stability of lotus seed emulsion,increasing the amount of starch precipitation during storage.XN could not affect on the stability of lotus seed emulsion significantly,which might be related to the presence of protein,fat and other substances in the multi-component system,which influenced the anti-retrogradation effect of XN on starch.GG could significantly improve the stability of lotus seed emulsion,which was related to the fact that GG effectively inhibited the long-term retrogradation of lotus seed.The results provide an important theoretical basis for the application of LS and hydrocolloids in food production.?5?Study on the digestibility of Lotus seed starch-chitosan blendsCompared with LS,LS-CS blends had a higher degree of structure ordering,suggesting that LS-CS blends might have the characteristics of slowly digestion.In order to verify that LS and CS can improve the starch digestibility in vitro,the effect of CS on the digestion of LS in vitro was studied in this chapter.The results showed CS could significantly slow down the in vitro digestion rate of LS,the content of rapidly digestible starch decreased and the content of slowly digestible starch increased when compared to LS alone.The solubility,swelling and viscosity of LS were reduced by CS,which indicated the granule structure of LS-CS blends was more stable than LS alone,that was one of the reasons for the improvement of its anti-enzymatic hydrolysis.In addition,CS caused the increases on amylose content and the ordered structure content,as well as a decrease in surface roughness,which reduced the effect of digestive enzymes on starch substrates,resulting in the slower digestion rate of LS-CS blends.It confirmed that CS combined with autoclaving-cooling treatment could alter the digestibility of LS synergistically.The results provide a scientific basis for the development of starch food with slow digestion.