Plasticizer migration from packaging films to foods can raise health concerns especially when foods are
heated in microwaves with their packaging. To inhibit the plasticizer migration, starch-based films were
prepared by controlling the micro-structure of esterified starch films with various degrees of substitution
(DS), and diethyl phthalate (DEP) was added. The DEP migration after microwave heating, and the
interaction between the plasticizer and starch molecules, and the aggregation structure of starch films at
nanometer scales were investigated. The data showed that the esterified starch film with the DS of 1.81
had the lowest amount of DEP migration compared with other films (DS 1.17, 1.42, 2.27, and 2.61). The
starch films with higher DS showed increased X-ray scattering intensity with a B-type starch scattering
pattern. The high DS enhanced the order and compactness in both crystalline and amorphous regions of
the film, and increased the distance between crystalline regions. In addition to the change in its aggregation
structure, the increase of DS weakened intermolecular interaction between starch molecules,
but increased the interaction between DEP and starcheester molecules. Our approach offered a balance
of structural integrity and intermolecular interaction. Plasticizer migration was successfully reduced by
controlling the DS of esterified starch film with a strong interaction between DEP and starcheester
molecules, better organized crystalline structure, and more compact and better ordered micro-region
aggregation structures with suitable distance between them.