Zein has widespread applications in food, medicine, biological materials, and the textile industry, but its use is limited to some degree due to the insolubility in water. To overcome this drawback, zein was phosphorylated by POCl3 and its physical properties of modified zein, such as viscosity, isoelectric point, as well as stability in acid and alkali were determined. Secondary and tertiary structures of zein before and after phosphorylation were measured by circular dichroism (CD), while thermal stability was determined using differential scanning calorimetry (DSC). The results showed that in 80% ethanol solution, the isoelectric point (PdI) of zein was at pH 5.97 and particle size was 1436 nm. Post modification, phosphate was combined with zein by O- and N- phosphate bonds, which mainly formed O-phosphate bonds under acidic conditions (pH 5.0) and N-phosphate bonds under neutral and alkaline conditions (pH 7.0 and 9.0). In addition, the viscosity of modified zein increased, the isoelectric point showed acidic shift, α-helix structure content reduced, and glass transition temperature increased.
