Physicochemical Properties Of Oat Starch Fatty Acid Esters And Application In Lactobacillus Plantarum Microcapsules

In this study,oat starch was used as raw material to prepare the different oat starch fatty acid esters by microwave-assisted method.Taking the preparation of OS-S as an example and choosing DS as an evaluation index,the preparation process was optimized;the differences of structure and physicochemical properties between oat starch and different starch fatty acid esters were studied;the application of OS-M in Lactobacillus plantarum microcapsules was studied.The results of this study were as follows:Preparation of oat starch fatty acid esters:OS-S was prepared by microwave-assisted method with oat starch and Stearic acid as raw material.The preparation process of OS-S was optimized by the single factor experiment and the response surface design.The optimum conditions were determined as follows:the addition of pullulanase was 4 u/g,oat starch concentration was 7%,the addition of fatty acid was 9%and the microwave time was 5 min.The DS of OS-S was 0.03455.OS-P,OS-M and OS-O were prepared under the optimum technological conditions,and DS was 0.04393,0.05465 and 0.03823,respectively.The structure and physicochemical properties of OS,OS-S,OS-P,OS-M and OS-O were studied.The structure of different starch fatty acid esters were characterized by infrared spectroscopy and XRD.The results of infrared spectroscopy analysis showed that OS-S,OS-P,OS-M and OS-O exhibited new stretching vibration characteristic absorption peaks at 1 710cm^-1,1 712 cm^-1,1 716 cm^-1 and 1 712 cm^-1,respectively,indicating that the formation of oat starch fatty acid esters;X-ray diffraction results showed that the crystalline morphology of oat starch changed from A to V after interaction with different fatty acids;starch-iodine scanning spectroscopy showed the formation of starch fatty acid esters;comparing with oat starch,the size of oat starch fatty acid esters increased significantly,starch particles accumulated together and showed porous network structure.The results of particle size analysis showed that starch granules increased significantly compared with oat starch;DSC patterns showed that the gelatinization temperatures of the different oat starch fatty acid esters was higher than90?,and the thermal stability was significantly improved;the water and oil absorption capacity of oat starch were significantly improved after introducing the ester group of fatty acids;at the same time,the introduction of different hydrophobicity in oat starch after esterification,oat starch was given certain emulsifying property,and OS-M had the best emulsifying property and emulsifying stability.The transparency of oat starch and oat starch fatty acid esters was studied.The results showed that the transparency of starch fatty acid esters increased with the shortening of carbon chain length of substituted fatty acids,and the transmittance of OS-M was the highest.With the prolongation of storage time,the transparency of fatty acid esters decreased gradually.The digestibility of oat starch and oat starch fatty acid esters in vitro were studied.The results showed that the content of resistant starch increased gradually with the decreasing of the length of fatty acid carbon chain,and the content of resistant starch in OS-M was the highest.Based on OS-M's better adsorption and anti-enzymatic properties,it was applied to Lactobacillus plantarum microcapsules.OS-M was mixed with Lactobacillus plantarum to prepare microcapsules by the extrusion method.The optimum technological conditions for the first encapsulation were determined as follows:OS-M concentration was 3%,sodium alginate concentration was 2.5%,CaCl₂ concentration was 2%,and the absorption time was 40 min.The encapsulation rate of Lactobacillus plantarum microcapsules prepared under these conditions was 99.69%.Because of the poor gastrointestinal tolerance for the first-embedding microcapsules,the second-embedding was carried out on the basis of the above,and the gastrointestinal digestion simulation of the second-embedding Lactobacillus plantarum microcapsules was carried out.The results showed that the gastrointestinal tolerance of the second-embedding Lactobacillus plantarum microcapsules were better than the first-embedding microcapsules.After through gastrointestinal digestion simulation,the viability of the second embedded Lactobacillus plantarum microcapsules still remained above10⁶,which could satisfy the function of balancing intestinal flora.The storage stability of the second-embedding Lactobacillus plantarum microcapsules was studied.The results showed that the optimal storage temperature of the second-embedding Lactobacillus plantarum microcapsules was 4?.