甜菜果胶中性糖的水解方法及定量分析

A Hydrolyzing Method of Neutral Sugar in Sugar Beet Pectin and Their Quantitative Analysis

为测定甜菜果胶中性糖的种类及含量,建立了针对甜菜果胶中性糖的两步水解法.该法采用果胶酶、三氟乙酸(TFA)依次水解甜菜果胶的中性糖.首先,甜菜果胶被果胶酶水解为相对分子质量较小的组分;其次,在TFA作用下,中性单糖从甜菜果胶分子上逐步释放到水解液中.在受试的3种商业酶制剂中,果胶酶Rapidase C80因其酶解效果好、内源性单糖少等优点被选为目的果胶酶.研究结果表明,C80的最适酶解条件为50℃、pH5、15 h.在C80酶解的基础上,进一步研究TFA浓度、酸解温度、酸解时间对中性糖水解效果的影响.综合评价中性糖水解率与降解率的关系后,确定适宜的TFA浓度、温度、时间分别为1 mol/L、110℃、4 h.高效阴离子交换色谱(HPAEC)分析结果表明,两步水解法对鼠李糖的水解效果显著,且该法稳定性好、可重复性高,能够满足甜菜果胶中性糖定量分析的需要.

In order to determine the variety and contents of the neutral sugar in sugar beet pectin( SBP),a twostep hydrolysis method was proposed for the SBP. In the method,the neutral sugar in the SBP were sequentially hydrolyzed by using pectinase and trifluoroacetic acid( TFA). First,the SBP was degraded into the fractions of smaller relative molecular mass by pectinase. Second,the neutral sugar attached to the SBP were liberated into solution by TFA. Among three commercial pectinases,Rapidase C80 was selected as the objective pectinase because of its lower endogenous monosaccharide content and better hydrolyzing activity. It is found that the optimal hydrolysis parameters of C80 are 50 ℃,pH 5 and 15 h. Moreover,the effects of the TFA concentration,the temperature and the hydrolysis duration on the hydrolysis of the neutral sugar were further investigated. By compromising the hydrolysis rate and the degradation rate of the neutral sugar,suitable TFA concentration,temperature and hydrolysis duration were respectively determined to be 1 mol/L,110 ℃ and 4 h. The HPAEC analysis results show that the proposed method has a good effect in achieving rhamnose through hydrolysis,and it exhibits a good stability and a high repeatability,which means that this method can be used to quantitatively analyze the neutral sugar in the SBP.