双波长法测定木薯淀粉中直链和支链淀粉的含量

Separation and Purification of Amylose and Amylopectin from Cassava Starch and Content Determination by Dual-wavelength Spectrophotometry

目的:分离纯化木薯淀粉中的直链和支链淀粉,建立同时测定木薯淀粉中直链与支链淀粉含量的双波长法。方法:采用正丁醇结晶法分离纯化直链和支链淀粉,蓝值比较法表征直链与支链淀粉的纯度;根据双波长法原理,分别在测定波长624、538nm,参比波长440、750nm处测定木薯淀粉中直链与支链淀粉含量。结果:分离纯化得到的直链与支链淀粉蓝值分别为0.979和0.144,分别落在0.8～1.2与0.08～0.22范围内,表明纯化后木薯直链与支链淀粉的纯度较高;直链淀粉在0～80mg/L质量浓度范围内其碘复合物与吸光度呈线性关系(r=0.9992),支链淀粉在0～220mg/L质量浓度范围内其碘复合物与吸光度呈线性关系(r=0.9995)。结论:正丁醇结晶法能有效地分离木薯直链与支链淀粉;双波长法操作快速、准确,无需分离即可同时测定木薯淀粉样品中直链和支链淀粉含量。

Objective： To separate and purify amylose and amylopectin from cassava starch and to establish a dual-wavelength spectrophotometric method for determining their contents.Methods： The amylose and amylopectin in cassava starch were separated by n-butanol crystallization method.The purity of amylose and amylopectin was characterized by blue value of starch-iodine complex.According to the principle of dual-wavelength spectrophotometry method,the contents of amylose and amylopectin in cassava starch were determined at the selected wavelengths of 624 nm and 538 nm with respective reference wavelengths of 440 nm and 750 nm.Results： The blue values of purified amylose and amylopectin were 0.979 and 0.144,respectively,which were in the distribution range of corresponding standard samples.A high purity of cassava amylose and amylopectin was achieved.An excellent linear relationship between starch-iodine complex and absorbance was achieved in the range of 0-80 mg/L（r=0.9992） for amylose and 0-220 mg/L（r=0.9995） for amylopectin.Conclusion： n-butanol crystallization method amylose and amylopectin from cassava starch.The developed dual-wavelength spectrophotometry method is convenient,accurate and suitable for determining the contents of amylose and amylopectin in cassava starch simultaneously.