Structural and functional characteristics of esterified starch and microencapsulation for urate-lowering probiotic: Effect of hydrophobic side-chain length

Esterified starch exhibits desirable freeze-thaw stability and emulsifying properties; however, there are limited reports on how the side-chain length of the acid anhydride affects the antifreeze activity and microencapsulation ability of starch. In this study, four types esterified starch with different hydrophobic chains were prepared and their physicochemical characteristics were explored. The results indicated that acid anhydride modification decreased the amylose content and relative crystallinity of native starch and altered its surface composition. Dodecenyl and hexadecenyl succinic anhydrides rendered the starch with relatively low degree of substitution but strong surface hydrophobicity (>120°). The order of anhydrides with different chain lengths to impart emulsifying ability to starch was dodecenyl succinic anhydride > octenyl succinic anhydride > hexadecenyl succinic anhydride > maleic anhydride, whereas the O/W Pickering emulsion storage stability of hexadecenyl succinic anhydride-esterified starch significantly decreased. Moreover, modified starches with superior freeze–thaw stability for microencapsulation improved the freeze-drying resistance of urate-lowering probiotics. Meanwhile, the encapsulated probiotics which passage through a simulated digestion exhibited superior xanthine oxidase inhibition. These results indicate that the appropriate chain-length acid-anhydride-modified starch is a promising cryoprotectant for frozen products.