Determination of amylase and amylopectin in hullessbarley from different habitats and varieties by dual-wavelength colorimetric method

A more simple, accurate dual-wavelength colorimetric method was developed to determine the contents of amylose and amylopectin in hullessbarley from different habitats and varieties. It was replaced the previous complicated sample pre-treatment process. The reaction solution that reacted by two ingredient of starch and iodine reagents were scanned from 450 nm to 900 nm by UV spectrophotometer to determine its detection wavelength and reference wavelength in the same coordinate system which according to the principle of the dual-wavelength colorimetry——the difference was proportional to the concentration of solute while there were two absorption peaks at two different wavelengths from the same solute in the solution, as well as characteristic of blue appearance that amylase encountered with iodine reagents and purple red as amylopectin. The results indicated that the detection wavelength and reference wavelength were 560 nm and 506 nm for amylase, 545 nm and 722 nm for amylopectin, respectively. The method had good linear relationship within the ranges of 0.20 ⁰. 59 mg for amylose ( R2= 0. 9993) , 0. 50 ~ 3. 00 mg for amylopectin ( R2= 0. 9995) , respectively. The average recoveries (n=9) were 91.14% (RSD=1.70%) for amylose and 91.73% (RSD=2.25%) for amylopectin. The assay demonstrated that the method had adequate simple, accurate, good stability and reproducibility. It was suitable for the determination of amylose and amylopectin contents in hullessbarley. In addition, it could be used to assist the quality evaluation of hullessbarley.