| Starch is one of the most abundant polysaccharides in nature.It can react with fatty acids to form a single helix starch-fatty acid complex,which can delay the retrogradation of starch.Because of its high amylose content,high amylose shows different physical and chemical properties from ordinary starch,with high added value,so it has a very broad application prospect in food,textile,papermaking,packaging and medical.However,when used as raw material,high amylose starch has the characteristics of dense structure,insolubility in most solvents and high gelatinization temperature,which limits its commercial utilization.In recent years,ionic liquid（IL）,as a new type of green solvent,has many advantages over traditional organic solvents,and has been gradually applied in the study of starch dissolution.In this thesis,the effect of water/IL ratio and alkyl chain length of ionic liquid on the structure and properties of starch was investigated under different temperature conditions using high amylose maize starch（HAMS）as the object.using ionic liquid-treated HAMS as the main molecule and lauric acid（LA）as the guest molecule,and the correlation between the amount of complex formation and starch retrogradation at different storage temperatures was explored.The main conclusions are as follows:（1）The effects of different ratios of water/ionic liquid on HAMS dissolution behavior at room temperature were studied.The intensity of polarized cross of starch particles after ionic liquid pretreatment was weakened,and the structure of starch particles was damaged in different degrees under scanning electron microscope.The starch samples treated with ionic liquid were characterized by X-ray diffraction.The results showed that the crystal structure type of HAMS treated with different water/ionic liquid ratio did not change,but the diffraction intensity of the main diffraction peak was reduced.The relative crystallinity decreased from 15.89%（without ionic liquid treatment）to 7.50%.In addition,ionic liquid pretreatment destroyed the short-range ordered structure of starch.Thermogravimetric analysis showed that the thermal stability of HAMS decreased after treatment with ionic liquid compared with raw starch.（2）HAMS-LA complexes were prepared by complexing HAMS treated with different ratios of water/ionic liquid mixtures with LA under heating conditions.The crystal structure of starch changed from B type to B+V type.The results of Fourier infrared and Raman spectra show that the pretreatment of ionic liquid improves the short-range molecular order of the complex.The ratio of water to ionic liquid has a significant effect on the structure and properties of starch-fatty acid complex.When the ratio of water to ionic liquid is 0.25:1,the characteristic diffraction peak of V-type complex is the strongest,the relative crystallinity increases to 17.56%,and the formation of the complex has the highest enthalpy value（1.92 J/g）.（3）The effect of alkyl chain length of ionic liquids on the dissolution behavior of HAMS under heat treatment conditions were studied.With the increase of treatment temperature,the dissolution effect of ionic liquid on HAMS was significantly enhanced.When starch was treated at 70℃,the polarizing cross disappeared completely and the order of short-range molecules decreased significantly.The value of 1047 cm-1/1022 cm-1 decreased from 0.859（without ionic liquid treatment）to 0.143.Under the condition of 30℃,the particle structure of starch was destroyed by ionic liquid treatment,but the dissolution effect of ionic liquid with different alkyl chain lengths was not significantly different.Under the condition of 50℃,the characteristic diffraction peak strength of ionic liquid to HAMS and the order degree of short-range molecules decreased with the increase of cationic alkyl chain length.（4）Pretreatment temperature and alkyl chain length of ionic liquid have significant effects on the structure and physicochemical properties of HAMS-LA complex.The rheometer showed that the viscosity of aqueous solution of ionic liquid decreased with the increase of system temperature and increased with the increase of alkyl chain length.At 30℃,the relative crystallinity of the complex pretreated with 1-propyl-3-methylimidazole chloride with medium alkyl chain length is slightly larger than that of 1-ethyl-3-methylimidazole chloride and 1-butyl-3-methylimidazole chloride.Under the conditions of heat treatment at 50℃and 70℃,with the increase of alkyl chain length of ionic liquid,the complex presents a more sharp and stronger characteristic diffraction peak.At 70℃,the relative crystallinity of the complex formed after1-butyl-3-methylimidazole chloride treatment increases to 29.08%,and the gelatinization enthalpy increases with the increase of alkyl chain length of ionic liquid.The content of typeⅡcomplex increased gradually.Finally,the relationship between the amount of complex formation and the regenerative properties of starch was investigated under freezing,refrigeration and normal temperature.With the extension of storage time,the intensity of the diffraction peak near 17°of the starch samples increased.The retrogradation kinetics showed that the retrogradation rate（k）of the samples stored at-18℃and 25℃was lower than that at4℃.The melting enthalpy of the recrystallization of amylopectin decreased after the addition of LA to form HAMS-LA complex.After the ionic liquid pretreatment,the formation of starch fatty acid complex increased,the diffraction intensity of B-type characteristic peak decreased,and the retrogradation rate（k）of starch was the lowest. |
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