Preparation and characterization of modified starch granules with high hydrophobicity and flowability

Normal cornstarch (NC) was chemically modified by octenylsuccinic anhydride (OSA) and Al2(SO4)3. The effects of the concentration of NaOH, OSA, and Al2(SO4)3 on the properties of modified starch(OS-starch-Al) were investigated. The OS-starch-Al was characterized by repose angle, activation index, inductively coupled plasma-atomic emission spectrometry (ICP-OES), light microscopy, SEM, FT-IR, and 27Al NMR. The results showed that pH 4 was the optimum condition for Al3+ cross-linking with OS-starch and for obtaining high flowability and hydrophobicity. When the concentration of OSA and Al2(SO4)3 was 2%, the OS-starch-Al was characterized by high flowability. A concentration of 4% OSA and Al2(SO4)3 yielded the highest activation index. The moisture content affected the flowability of native NC, but had a minor effect on OS-starch-Al. SEM and polarized microscopy revealed that the modification had slight effects on the crystalline structure and morphology of NC. During the preparation, some dust particles functioning as flow additives were produced on the surface of starch granules. The results of FT-IR, ICP-OES, and 27Al NMR confirmed the formation of ester group and the cross-link with Al3+.