Preparation,Characterization And Encapsulation Ability Of Linear Dextrin

In this paper,linear dextrin(LD)was obtained from amylose by optimizing the conditions of enzymatic hydrolysis of α-amylase.LD was fractionated into three LD fractions with different degree of polymerization(DP)by gradient alcohol precipitation,and the dominating chain length of three LDs was determined by high-performance anion exchange chromatography(HPAEC).Then arachidonic acid/LD(ARA/LD)and geranic acid/LD(GA/LD)composites were formed by optimizing the conditions of the encapsulation process.The encapsulation ability of LD with different chain length was investigated by Fourier transform infrared(FTIR),thermogravimetric analysis(TGA),X-ray diffraction(XRD),atomic force microscope(AFM)and in vitro digestion.This study is intended to elucidate the encapsulation regulation of LD with different DP values.(1)The optimum conditions of preparation of LD by α-amylase hydrolyzed the amylose were determined by single-factor and orthogonal experiment: the additive amount of α-amylase was 1.0 U/g,the enzymatic hydrolysis time was 20 min and the amylose emulsion concentration was 1.0%,the yield of linear dextrin with the DP value between 18-35 was 65.33%.LD components of the DP value between the 30-35,24-29 and 18-23 were collected by gradient alcohol precipitation,and refer to as 65 LD,70LD and 75 LD,respectively.The results of moisture content and solubility of LDs indicated that the moisture content and solubility of LD were increased with the chain length of LD shortened.In addition,the crystal structure of LD was B-type,and the relative crystallinity was decreased with shortening the chain length of LD.(2)The influence of LD with different chain length on the physicochemical properties of ARA/LD and GA/LD composites was investigated by using encapsulation rate,FTIR,differential scanning calorimetry(DSC),TGA,XRD and AFM.FTIR confirmed that ARA/LD and GA/LD composites were formed by hydrophobic interaction.The results of DSC and XRD further verified the formation of ARA/LD and GA/LD composites,and the molecular arrangements of ARA/65 LD and GA/75 LD composites were more ordered and compact than other ARA/LD and GA/LD composites.Depending on the results of AFM,ARA/65 LD composite showed an oval spherical-like structure and the granules were evenly dispersed.The morphological structure of ARA/LD was inclined to form agglomerates with the chain length of LD shorted.While the microstructure of GA/65 LD displayed a rod-like aggregation,and the GA/75 LD composite showed a tightly structure and the granules were spherical.(3)The optimal processing condition of ARA/65 LD and GA/75 LD composites were discussed by means of response surface methodology and some single factor experiments as follows: the molar ratio between LD and ARA was 1:2,the reaction time was 12 h,and the encapsulation temperature was 90 °C,the encapsulation rate of ARA reached the maximum(32.91%),while the molar ratio between LD and GA was 1:1,the reaction time was 18 h,and the encapsulation temperature was 90 °C,41.68% of GA was encapsulated by 75 LD.The results of FTIR and XRD suggested that the ARA/65 LD and GA/75 LD composites were formed.In vitro digestion experiments exhibited that the ARA and GA had slow release properties after forming the ARA/65 LD and GA/75 LD composites.Compact structures of composites reduced the stimulation of the gastric digestion to ARA and GA.After the composites were delivered into the intestinal tract,ARA and GA would be released gradually from the composite under the hydrolyzation of pancreatin.The retention of ARA after complexing with 65 LD was 84.37% and the retention of GA was obtained from GA/75 LD composite,which reached 90.34%.The results of photochemical stability and antioxidation test showed that the degradation degrees of ARA and GA by UV light were reduced effectively,as well the accessibility of oxidization was weakened after ARA and GA were wrapped in LD.Overall,the longer chain LD displayed the better encapsulation efficiency with the longer chain ARA,while the complexing capability of shorter chain LD with GA was better than other LDs.