Green preparation method for hydrophobic fatty acid ester of starch (FES)

The invention discloses a green preparation method for hydrophobic FES. The method comprises the following steps: adding the raw material of dried starch into mixed ionic liquid of 1-butyl-3-methylimidazole acetate and 1-butyl-3-methylimidazole tetrafluoroborate, and carrying out heating and stirring at a constant temperature under a nitrogen atmosphere; cooling an obtained solution, adding lipase and fatty acid methyl ester, wherein the usage amount of lipase accounts for 3 to 15% of the mass of the dry basis of starch and a mol ratio of fatty acid methyl ester to starch is 1:1 to 1: 5, and allowing the solution, lipase and fatty acid methyl ester to undergo a reaction at a temperature of 50 to 80 DEG C for 1 to 5 h; and after the reaction is finished, adding anhydrous ethanol for rinsing and centrifugation after the solution is cooled, removing supernatant, and drying an obtained precipitate at a temperature of 35 to 50 DEG C for 40 to 48 h so as to obtain FES disclosed in the invention. The product of FES has good thermoplasticity, hydrophobicity and biodegradability and has an application value in a wide variety of industries like microcapsule wall materials, biodegradable materials and foodstuffs.