Abstract:Linear dextrin aggregates comprising different chain length distributions were prepared from high-amylose corn starch modified using hydrochloric acid and pullulanase. Docosahexaenoic acid (DHA) microcapsules were prepared, and the effects of chain length distribution on the ordered structure, encapsulation efficiency, oxidation stability and digestion resistance of the microcapsules were systematically studied. The results showed that the proportion of long-chain linear dextrin (degree of polymerization > 100) in the linear dextrin aggregates decreased from 95.22% to 65.76%, whereas the proportion of short-chain linear dextrin (degree of polymerization: 10~100) increased from 4.62% to 33.73% after 0~96 h of acid hydrolysis. The content of short-range ordered structures in the microcapsules increased with the proportion of short-chain linear dextrin, indicating that reducing the chain length is beneficial to the formation of the linear dextrin-DHA complex and double helix structures. The content of V-type crystal structure in microcapsules gradually increased from 1.18% to 8.44% with the increase in short-chain linear dextrin content, whereas the content of B-type crystal structure decreased from 7.84% to 2.57%. Linear dextrin aggregates that contained 22.17% short-chain linear dextrin and 77.46% long-chain linear dextrin produced microcapsules with the best encapsulation efficiency, oxidation stability, and digestion resistance. The results showed that the formation of the double helix structure and the linear dextrin-DHA complex can be promoted by shortening the molecular chain length of linear dextrin, thereby improving the performance of DHA microcapsules.
