| Starch has important applications in food and other industries.However,due to the limitation of physical and chemical properties of raw starch,it is often necessary to compound it with hydrophilic colloids in the actual processing process to improve its gelatinization,aging,digestion and other properties.At present,the modified non-starch polysaccharides have not been applied to the study of starch processing characteristics.In this paper,potato starch is used as the raw material,and Lycium barbarum L.leaves polysaccharides are selected for sulfation and carboxymethylation modification,to explore the role of the two modified polysaccharides in starch processing properties,and to analyze the mechanism of different effects.The main conclusions are as follows:1.Use chemical modification to obtain different Lycium barbarum L.leaves polysaccharides.First,the high temperature hot water method was used to extract polysaccharides and processed to obtain refined Lycium barbarum L.leaves polysaccharide LP.Sulfation and carboxymethylation were used to modify LP to obtain sulfated polysaccharide SLP and carboxymethylated polysaccharide CLP with substitution degrees of 1.04 and 0.54,respectively.The vibrational shrinkage of S=O,C-O-S and COO-appearing in the infrared spectrum and the chemical shift of the anomeric carbon in the nuclear magnetic resonance spectrum indicated the existence of the characteristic peak of the derivative and the modification of the polysaccharide.In addition,through size exclusion chromatography?SEC?equipped with a differential detector?RI?and a multi-angle laser light scattering instrument?MALLS?,it was found that the Lycium barbarum L.leaves polysaccharide LP has a rod-like structure,and the modified conformations were changed to random linear SLP and globular structure CLP.2.Lycium barbarum L.leaves polysaccharide and its derivatives had a significant effect on the gelatinization of potato starch.The results of rapid viscosity analyzer?RVA?and differential calorimetry?DSC?showed that the addition of polysaccharide significantly reduced the gelatinized viscosity of potato starch,in which the peak viscosity of SLP and CLP compound starch,were reduced by 33.53%and 20.61%respectively,and the energy required to destroy potato starch granules during gelatinization?H increased from 3.865 J/g of the original starch to 4.579 J/g and4.102 J/g,respectively.It showed that in the process of potato starch gelatinization,LP and its derivatives?SLP and CLP?competed with starch for water molecules and combined with it,which affected the starch gelatinization process.And because LP and its derivatives reduced the swelling ability of starch,it affected the action site of digestive enzymes in starch granules,resulting in an increase in the content of slow-digestible starch?SDS?in potato starch.3.The effects of Lycium barbarum L.leaves polysaccharides and their derivatives on potato starch were different.Fourier transform infrared spectrum?FTIR?results showed that due to the different chain structure of the polysaccharide aqueous solution,the infrared intensity of the compound starch was different.Among them,the rod-shaped LP and the random linear SLP acted on the surface of the potato starch,resulting the particle surface at 3500 cm-1?-OH absorption peak?was enhanced,and the spherical CLP acted on the inside of the potato starch granules,resulting in the decrease of the internal polymerization secondary structure characteristic peaks 2900 cm-1,1412cm-1 and 1022 cm-1.In addition,the addition of polysaccharides caused incomplete swelling of the starch granules,and also reduced the crystallinity.The hardness of the starch gel added with CLP was reduced from 23.8 N to 7.6 N,and the crystallinity was reduced from 2.25±0.02%to1.28±0.03%,which had the most obvious effect of inhibiting aging and regeneration.In summary,after being modified by sulfation and carboxymethylation,the conformation of the aqueous solution of Lycium barbarum L.leaves polysaccharide changed.While competing for water molecules to inhibit potato starch gelatinization,it also significantly affected starch aging and digestion properties.It provides a theoretical basis for the application of modified polysaccharides in starch-based foods. |
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