Octenyl succinic anhydride modified starch with excellent emulsifying properties prepared by selective hydrolysis of supramolecular immobilized enzyme

Octenyl succinic anhydride modified starch is a common green and safe emulsifier. Although the conventional pretreatment method of free enzyme hydrolysis increases the hydroxyl content on the starch surface, thus improving the grafting degree of octenyl succinic anhydride and the amphiphilicity of the modified starch, the amylose and amylopectin structures are indiscriminately hydrolyzed, reducing the emulsion stability of modified starch. In this work, α-amylase organic-inorganic hybrid nanoflower biocatalyst is designed and synthesized for pretreatment of synthetic octenyl succinic anhydride modified starch. The α-amylase organic-inorganic hybrid nanoflower biocatalyst with a unique micro-nano spatial structure can selectively hydrolyze the amylopectin and protect the amylose of starch. The amylose ratio of starch pretreated by nanoflower biocatalyst is about twice that of starch pretreated by free enzyme, reaching 22.62 %. Meanwhile, the granular structure of starch is not damaged. The obtained octenyl succinic anhydride modified starch exhibits a high degree of substitution, up to 0.0213. The emulsion prepared with this modified starch maintains excellent emulsifying properties and stability. This study provides a novel strategy for the preparation of octenyl succinic anhydride modified starch with excellent emulsifying properties, which promote the application of octenyl succinic anhydride modified starch in food, pharmaceutical and cosmetic industries.