Preparation and properties of benzyl corn starches

Benzyl corn starches (DS 0.02-0.16) were prepared by reacting starch with benzyl chloride in an alkaline aqueous medium at 65 °C. and the pasting properties of the starches were investigated. Reaction yield with 20% benzyl chloride (based on starch weight) tor 12 h was increased from 26.7% to 60.5% as the NaOH addition increased from 3% to 8% (based on starch weight), and became relatively constant thereafter. With 20% benzyl chloride and 8% NaOH, degree of substitution (DS) reached 0.16. Light transmittance and viscosity of starch paste were decreased as DS increased. Low viscosity and opaqueness of the paste indicated that the benzyl groups increased hydrophobicity, and reduced solubility of the starch. Onset temperature (T_o) for starch melting measured by a Differential Scanning Calorimeter thermogram was decreased as DS increased up to 0.1. But above DS 0.1, T_o increased. Melting enthalpy was also decreased as DS increase because of the incomplete gelatinization. Solubility in aqueous methanol (80%) increased near 2% as DS reached 0.16. Maximum wavelength and absorbance of the iodine complexes of benzyl starch were decreased with benzylation.