Determination of amylose and amylopectin in pumpkin with dual-wavelength colorimetric method

Dual-wavelength spectrophotometry was applied to the determination of amylose and amylopectin from pumpkin. N-butanol crystallization separation and purification of pumpkin in the linear and amylopectin,and content of them were mensurated. The results showed that the blue values of linear and amylopectin isolated and purified were 0.874 and 0.196,respectively. According to the principle of dual-wavelength spectrophotometry and scanning spectra,the contents of amylose and amylopectin in pumpkin were determined at the selected wavelengths of 645 and 565 nm with respective reference wavelengths of 495 and 730 nm. The amylose in pumpkin samples accounted for 21.64%,the amylopectin was 50.19% and the total starch was 71.83%. The RSD was 0.97% and 1.06%,respectively. The average recovery of amylose and amylopectin were 98.62% and 99.42%,respectively,while detection limit were 0.0116 and 0.0644 mg/mL. N-butanol crystallization method could separate and purify of amylose and amylopectin in pumpkin effectively. The detection method could obtain three kinds of starch content simultaneously. The developed dual-wavelength colorimetric method was not only cost-saving and efficient for determination of amylose and amylopectin,but also provide a basis for research on physicochemical properties of starch in pumpkin.