Determination of Amylose Content by Dual Wavelength Method

Determination of Amylose Content by Dual Wavelength Method

Since amylopectin also forms a complex with iodine, this complex absorbs light of the same wavelength as the amylose-iodine complex, resulting in a higher amylose content than the actual value. In addition, the single wavelength method can only determine the content of amylose in cereals, and the food quality of grain is also related to the content of amylopectin and the ratio of amylose and amylopectin. The dual wavelength method can be used to obtain three indexes of amylose, amylopectin and total starch at the same time, which saves time and effort, and has high work efficiency. It is suitable for mass analysis. Below we have a thorough understanding of the dual-wavelength method by comparing the principle of the dual-wavelength method with the determination of amylose content with an amylose content meter.

Dual-wavelength colorimetry principle: If a solute in a solution absorbs at both wavelengths, the difference in absorbance at the two wavelengths is directly proportional to the solute concentration. The standard solutions of amylose and amylopectin formulated with the standard sample corresponding to the sample to be tested are reacted with iodine, respectively, and then scanned in the same coordinate system (400-960 nm) or as an absorption curve to determine the straight chain. The measuring wavelength and reference wavelength of starch λ2, λ1, the measuring wavelength of amylopectin and the reference wavelengths λ4, λ3. Then the sample to be measured and iodine color, in the selected wavelength for 4 times colorimetry, and then use amylose and amylopectin standard curve can be obtained in the sample of the two types of starch content. Because the difference in absorbance of the sample at two wavelengths is measured, the mutual influence of the two types of starch absorption background is subtracted, so the sensitivity and selectivity of the assay can be improved. Of course, we also need to use the results measured by amylose meter to compare, in order to determine the accuracy of the dual wavelength method.

Dai Shuang et al. compared the determination of wheat straight and amylopectin content by single-wavelength method and dual-wavelength method. The results show that the dual-wavelength method can effectively eliminate the interference of other substances, and the measurement result is better than the single wavelength method. The recoveries of amylose obtained by Fammingshun et al. using the dual-wavelength method ranged from 95.0% to 101.7%, and the recoveries of amylopectin were 98.8% to 103.2%, indicating that the dual-wavelength method has good reproducibility and relative standard deviation. less than 1%. In addition, if we want to determine the content of amylose more quickly and conveniently, we can measure it with an amylose analyzer.

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