The invention discloses a method for preparing
modified starch, and belongs to the field of
starch processing. The method includes uniformly mixing
starch and water with each other to obtain first mixtures and pasting the first mixtures; adding
tetrasodium pyrophosphate into the first mixtures, uniformly mixing the
tetrasodium pyrophosphate and the first mixtures with one another to obtain secondmixtures, allowing the second mixtures to stand still, cooling the second mixtures and carrying out
freeze drying on the second mixtures to obtain dry substances; carrying out ball-milling on the drysubstances and
beeswax, then uniformly stirring the dry substances, the
beeswax and absolute ethyl
alcohol to obtain third mixtures; placing the third mixtures in a
steam explosion device and carryingout
steam explosion on the third mixtures to obtain explosion substances; mixing the explosion substances and
hydrogen peroxide with one another and carrying out oxidation treatment on the explosionsubstances and the
hydrogen peroxide; adding
ethylene glycol into the explosion substances and the
hydrogen peroxide to obtain fourth mixtures, allowing the fourth mixtures to stand still and carryingout spray-
drying on the fourth mixtures while the fourth mixtures are hot so as to obtain spray-
drying substances; carrying out stirring reaction on the spray-
drying substances, aluminum
chloride andacetyl
chloride to obtain reaction products; adding
tyrosine into the reaction products, stirring the
tyrosine and the reaction products to obtain fifth mixtures, cooling the fifth mixtures until thetemperatures of the fifth mixtures reach the
room temperature and discharging discharged substances; carrying out
freeze drying on the discharged substances, washing, drying, smashing and sieving thedischarged substances to obtain sieved particles so as to obtain the
modified starch. The method has the
advantage that the
modified starch is good in freeze-thaw stability and excellent in film forming property.