Effect of Physicochemical Modifications on Antioxidant Activity of Water-soluble Chitosan

Water-soluble chitosan was processed using ultrasonication, microfluidisation and homogenisation to modify its physicochemical properties. The effect of using sonicated chitosan on formation of chitosan-glucose conjugates was investigated. Untreated and sonicated chitosan conjugates were prepared under varying reaction conditions (such as ratios of reactants, pH and temperature). The conjugates formed were evaluated for colour development and antioxidant activity. For both untreated and sonicated chitosans, the reactivity was found to be higher at pH 6.0/121 A degrees C than at pH 4.9/121 A degrees C. The reactivity was found to be lower at 105 A degrees C at both pH conditions than at 121 A degrees C. This clearly demonstrated the greater reactivity at higher temperature irrespective of the reaction pH. Antioxidant activity studies indicated that the conjugates formed at 121 A degrees C had higher activity. Although sonication of water-soluble chitosan led to slightly enhanced viscosity indicating higher reactivity, it did not improve the antioxidant activity.