Abstract: By taking the corn starches of different amylose contents as raw materials and by fixing the dosage of propylene oxide and sodium hypochlorite,an oxidation and etherification dual-modification was carried out so as to reveal the effects of the modification sequence on the physicochemical properties of the corn starches.Then,the modified corn starches were analyzed in terms of transparency and Brabender viscosity,and they were characterized by means of XRD.Experimental results show that ( 1) the carbonyl and carboxyl of the oxidized-hydroxypropylated starches have higher molar substitution degrees,while the hydroxypropyl of the hydroxypropylated-oxidized starches has a higher one; ( 2 ) the transparency of the oxidized-hydroxypropylated starches is higher than that of the hydroxypropylated-oxidized starches; ( 3) the peak viscosity of the hydroxypropylated-oxidized starches is higher than that of the oxidized-hydroxypropylated starches; ( 4) both the two kinds of modification do not change the crystal form of starch molecules; ( 5) the dual-modification is closely related to the modification order,and the first reaction plays a leading role; and ( 6) lower amylose content is beneficial to the oxidative modification,while higher amylose content is beneficial to the hydroxypropyl modification.

Key words: starch, oxidation, hydroxypropylation, amylose content