Study On Exogenous Induction,Extraction And Edible Film Of Aloe Vera Polysaccharides

Aloe vera has the advantages of fast growth,easy cultivation and convenient processing,and its secondary metabolites are mainly aloe polysaccharides.Therefore,as a very ornamental garden species,it is important to study cultivation methods to induce the accumulation of secondary metabolites,cultivate Aloe vera with high aloe polysaccharide content,improve the utilization rate of Aloe resources,make Aloe vera widely cultivated and processed,enhance the value of Aloe vera itself and increase the production added value of Aloe resources,and promote its economic benefits.In this dissertation,cuttings were used to study the effect of exogenous substances to induce the accumulation of aloe polysaccharide in order to achieve an increase in the amount of polysaccharide per unit weight of Aloe vera;hydrothermal method was used to extract aloe polysaccharide,and the process was optimized in order to increase the yield of obtaining aloe polysaccharide;high performance gel permeation chromatography and ion chromatography were used,respectively,and the infrared scanning,rheological as well as analytical antioxidant studies were used to determine the structure and properties;the edible packaging film of aloe polysaccharide obtained was used to study the physicochemical properties of the film;blueberries were used as an example for application tests by immersion method to determine the fruit species during the freshness period,and the main results were as follows:1.Cuttings were used to study the induction of exogenous substances to accumulate Aloe vera polysaccharides.The effects of induction of salicylic acid,methyl jasmonate and mannitol on the polysaccharide content of Aloe vera were investigated separately using Aloe vera as the material:10 mg/L salicylic acid had the highest polysaccharide content of 107.62 mg/g;1.0mg/L methyl jasmonate had the highest polysaccharide content of 122.41 mg/g;25 g/L mannitol had the highest polysaccharide content of 95.45 mg/g.2.Process optimization and characterization of aloe polysaccharide extraction by hydrothermal method.A three-factor,three-level response surface analysis was performed on the basis of single factor,and the best process was verified as follows:liquid to material ratio 119:1m L/g,extraction temperature 107℃,extraction time 2.95 h.The maximum yield of aloe polysaccharide was 11.107%.The molecular weight and monosaccharide composition of the obtained aloe polysaccharides were determined by high performance gel permeation chromatography and ion chromatography,and the results were obtained by infrared scanning,rheological and antioxidant studies:the purity of aloe polysaccharides was high,the dispersion was homogeneous and stable,Mp was 23924 Da,Mw was 28802 Da,Mn was 20178 Da;the molar ratio of monosaccharides was mannose:glucose:arabinose:galactose=0.873:0.095:0.017:0.015;Newtonian fluid properties appeared when the concentration was 1%;the antioxidant ability of aloe polysaccharide was determined based on the scavenging effect of three free radicals.3.Preparation of edible packaging films of Aloe polysaccharides and their physicochemical properties.The films prepared by casting method and solvent evaporation method usingβ-hydroxy-β-methylbutyrate calcium（HMBCa）and nanocrystalline cellulose（CNCs）as cross-linking and reinforcing agents,respectively,were characterized and their properties were analyzed.Under the cross-linking effect,the HMBCa concentration was effective in the range of0.1-0.5 mg/m L to enhance the mechanical properties of the films,and the best performance was obtained by physicochemical analysis of AVP-0.25 HMBCa-CNCs films with good thermal stability decomposed at a temperature of 242.8°C,elongation at break of 17.45%,tensile strength of 39.37 MPa,solubility of 75%,absorbance value of 1.967 Abs at 243 nm,water vapor transmission rate of 17.63×10-11 g m^-1 s^-1 pa^-1,DPPH radical scavenging rate of 59.31%,and antibacterial effect.4.It was verified whether the aloe polysaccharide based film has fruit preservation effect.AVP-0.25 HMBCa-CNCs film showed good performance in terms of hardness,respiration rate,weight loss,relative conductivity,TSS and TA during blueberry preservation,and the shelf life of blueberry was extended by at least 6 days compared to that for the coated treatment.In conclusion,Aloe vera is a multifunctional fleshy herb with ornamental,edible and medicinal uses,and the accumulation,extraction and application development of its aloe polysaccharides can enhance the benefits of resource exploitation,lay the foundation for in-depth research on Aloe vera and its polysaccharides,and improve the economic value and production added value of resource production and exploitation.