An Optimized Procedure for Determining the Amylase/ Amylopectin Ratio in Common Wheat Grains Based on the Dual Wavelength Iodine-Binding Method

Wheat endosperm is mainly composed of starch consisting of amylose and amylopectin. The amylose/amylopectin ratio determines the starch properties. Thus, an appropriate method is essential to accurately measure this ratio. Here, we reported an optimized procedure based on the dual wavelength iodine-binding method that can accurately and conveniently determine the amylose/amylopectin ratio in wheat starch. This procedure is characterized by three aspects of advantages over the previously reported methods. Firstly, high purities of wheat starch standard can be easily isolated and thus replaces the commercial potato standard which is not suitable for determining wheat starch. Secondly, the comparison of wavelength pairs showed that the selection of wavelength pairs could be flexible. Finally, total starch of wheat grains can be extracted and used as measuring samples to eliminate the effects of non-starch impurities and obtain the amylose/amylopectin ratios with a single measurement. The amylose/amylopectin ratios of 28 wheat cultivars were analyzed using this improved procedure. Further, the data obtained from Megazyme assay kit confirmed the accuracies of this improved procedure. The results showed that the data generated by wheat standard were identical and were readily repeated. This optimized procedure allows efficient determination of amylose/amylopectin ratios in wheat starch.

Keywords: amylose, amylopectin, dual wavelength, wheat.