Dry Etherification for Starch Modification: Significantly Improve Its Hydrophobic Properties and Application in Bath Powder

ABSTRACT The effect of the dry etherification modification (DEM) method on the structural properties (i.e., molecular structure, crystal structure, morphology of the granules, thermal properties, and powder properties) of normal maize starch (NMS), and the prospects of etherified starch (HS‐HeD) in bath powder application were investigated. The results showed that DEM treatment mainly occurred on the surface of NMS and did not significantly destroy the original crystalline structure, which the characteristic A‐type crystalline peaks of the sample was appeared in XRD patterns at 15°, 17°, 18°, and 23° with a relative crystallinity of appropriate 33%, and remained the thermal properties and viscosity of NMS. In addition, after DEM treatment, the repose angle, the bulk density, and the compact density of the starch decreased from 45.06° to 26.10°, increased from 0.50to 0.61 g/mL, and increased from 0.81 to 0.89 g/mL, respectively. HS‐HeD had the highest hydrophobicity (contact angle, CA = 104.99°) at a pH level of 10.50, a reaction time at 120 h, and a reaction temperature at 120°C. It was further applied for the bath powder application. The performance of the laboratory prepared bath powder (with 80% HS‐HeD) was similar to that of the commercially bath powder (D50 value of 12.50 ± 0.02 µm and a composite score of 68.8), indicating a good suitability and avoiding the introduction of harmful metals. These findings demonstrated that DEM is a viable approach and HS‐HeD showed a valuable potential application in green daily necessities fields.