Preparation and in vitro digestibility of blueberry polyphenols microcapsules
[Objective]This study aims to study the extraction and purification of blueberry polyphenols and the preparation process of microcapsules,so as to provide scientific basis for the development of blueberry polyphenol microcapsules with sustained release function.[Method]The blueberry pomace separated from enzymolysis residue juice was used as the experimental material.The extraction and purification process of blueberry polyphenols was determined by comparing the effects of different extraction methods and different macroporous resins on the purification of blueberry polyphenols.On this basis,the blueberry polyphenols microcapsules were prepared by homogenization and freeze-drying.The embedding efficiency was taken as the main index,and the optimal preparation process of blueberry polyphenols microcapsules was determined by combining color and structure characterization,the in vitro gastrointestinal digestion characteristics of microcapsules were further analyzed.[Result](1)By comparing the fruit pomace and juice extracts of three blueberry cultivars,Gardenblue,Baldwin and Zhaixuan 4,the results showed that the total polyphenol contents of the fruit pomace extracts were higher than that of the juice extracts,with the highest being more than twice(Zhai Xuan 4).(2)The three macroporous resins HPD-300,HPD-100B and HPD-100 were selected by comparing adsorption and desorption capacities of 10 macroporous resins.(3)HPD-100B macroporous resin was selected to enlarge the extraction and purification experiment,and the blueberry polyphenol extract with purity of 71.4%was obtained.(4)On this basis,the embedment rate of blueberry polyphenols in the three wall materials of maltodextrin,soy protein and whey protein was investigated.It was found that the embedment rate of polyphenols in the soybean protein was the highest,and the compound of arabic gum could further improve the embedment rate of polyphenols.(5)Through the comparison of color differences,it was found that compared with the polyphenol extracts,the L* of microcapsule products decreased,while a* and b* increased,indicating a decrease in the brightness and blue color of microcapsules,and an increase in red color.(6)The results of scanning electron microscopy showed that compared with the polyphenol extract with lamellar structure,the microcapsules presented cross-linked spherical shape.In vitro digestion experiments showed that the release rate of polyphenol extract in gastric fluid and intestinal fluid was as high as 99.8%,while the release rate of polyphenol microcapsules in gastric fluid and intestinal fluid were 65.77%and 74.31 respectively.[Conclusion]The optimal preparation process of blueberry polyphenols is HPD-100B,HPD-300 or HPD-100 macroporous resin loaded with aqueous solution of the crude extract of blueberry residue,washed with 5 times bed volume of water to remove impurities such as sugars and acids,and then collected with 80%ethanol and concentrated under reduced pressure and freeze-drying to obtain blueberry polyphenols extract with the purity of 71.4%.The optimal preparation process of blueberry polyphenol microcapsules was using soybean protein and arabic gum as the optimal wall material whose solution concentration was 10%,and the soybean protein and arabic gum ratio was 3∶7.The core-wall ratio was 1∶5 and the pH of the core-wall mixture was 2.0.After homogenizing at 4 000 r/min for 10min and freeze-drying,the embedding rate of the prepared microcapsule attained 97.6%.The color of the microcapsule was low brightness with red and blue tones,the structure is crosslinked spherical,and the microcapsule has certain slow-release characteristic.
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