Effect of Microwave Radiation on the Physicochemical Properties of Normal Maize, Waxy Maize and Amylomaize V Starches

Abstract

Normal maize, waxy maize and amylomaize V starches were treated at a moisture content of 30% by microwave radiation. The results showed that the surface was porous and a cavity could be clearly observed at the center of the three starches. Microwave treatment increased the X-ray intensities of the major d-spacings of all starches and changed the X-ray pattern of amylomaize V from B to A+B. The swelling power (amylomaize V < normal maize < waxy maize) and solubility (amylomaize V < normal maize < waxy maize), syneresis (waxy maize > normal maize > amylomaize V) and the enthalpy of gelatinization (amylomaize V (B-type)> normal maize waxy maize (A-type)) decreased on this treatment. Microwave treatment increased the gelatinization transition temperatures (amylomaize V > waxy maize > normal maize) and the gelatinization temperature range (amylomaize V > normal maize ¡Ö waxy maize) of all starches. A rise in pasting temperature and a drop in viscosity of the three starches were observed after microwave irradiation. The viscosity patterns of waxy and normal starches remained unchanged, while that of amylomaize V starches changed from C to D on microwave treatment. The data showed that rearrangements restricted to sections of the starch molecules resulted in the formation of new crystallites of different stabilities and led to a more ordered crystalline array.