利用酶法测定稻米支链淀粉精细结构

Determination of Amylopectin Fine Structure in Rice by Enzymatic Method

支链淀粉是淀粉粒各级结构形成和稻米理化特性的主要决定因素。本研究对利用酶法测定稻米支链淀粉精细结构的酶解最适反应条件进行了探索和优化,结果表明,测定β-淀粉酶水解率时,对于0.1 g的支链淀粉,β-淀粉酶的最适用量为500 U,反应时间为48 h,反应温度为37℃;测定平均链长时,对于22 mg的支链淀粉,普鲁兰酶的最适用量为4 U,反应时间为24 h,反应温度为37℃;测定A∶B值时,对于1 m L质量浓度为1 mg/m L的β-极限糊精溶液,异淀粉酶的最佳用量为100 U,普鲁兰酶的用量为1 U,二者最适反应时间均为24 h。在条件优化的基础上,利用酶法对8个稻米品种支链淀粉的精细结构进行了测定,8个品种中β-淀粉酶水解率、平均链长、平均外链长、平均内链长、A∶B值的变幅分别为51.22%~62.86%、18.31~20.83、11.38~14.82、4.57~5.93、1.05~1.67。

Amylopectin is the determinant of starch granule structure and starch physiochemical properties. In this study, the optimum reaction conditions for enzymatic determination of amylopectin structure in rice were explored and optimized. The results showed that the optimal dosage of β-amylase was 500 U for 0.1 g of amylopectin, the reaction time was 48 h and the reaction temperature was 37℃ when the β- amylolysis was determined. For the 22 mg of amylopectin, the optimum dosage of pullulanase was 4 U, the reaction time was 24 h and the reaction temperature was 37℃ when the average chain length was determined. For 1 mL concentration of 1 mg/mL 13 - limit dextrins, the optimum dosage of isoamylase was 100U, the optimum dosage of pullulanase was 1 U, the reaction time of both was 24 h when the A： B value was determined. On the base of condition optimization, the fine structure of amylopectin in eight rice varieties was determined by enzymatic method. The results showed that the hydrolysis rate of β-amylase, average chain, length average exterior chain length, average internal chain length, A chain and B chain ratio varied from 51.22% to 62.86%, 18.31 to 20.83, 11.38 to 14.82, 4.57 to 5.93, 1.05 to 1.67, respectively