可视化移动反应界面滴定法测定豆浆中蛋白质的含量

利用移动反应界面滴定(moving reaction boundary titration, MRBT)技术可视化快速准确测定豆浆中的总蛋白质含量。在MRBT中,移动反应界面(moving reaction boundary, MRB)是由阴极液中的氢氧根离子和固定在聚丙烯酰胺凝胶(polyacrylamide gel, PAG)中的豆浆蛋白质分子形成,通过酸碱指示剂来指示MRB的移动。利用MRB移动速度(V_MRB)与蛋白质浓度存在的函数关系建立标准曲线。配对t检验MRBT测定结果与凯氏定氮相比在95%的置信区间内无显著性差异。MRBT测定所需时间为10 min左右,线性范围为2.0~14.0 g/L,检出限为0.05 g/L,日内相对标准偏差小于1.90%,日间相对标准偏差小于4.39%,回收率为97.41%~99.91%。此外,三聚氰胺等非蛋白质氮(non-protein nitrogen, NPN)的添加,对豆浆中蛋白质的测定结果影响较小。

Determination of total protein content in soya-bean milk via visual moving reaction boundary titration

A visual, rapid and accurate moving reaction boundary titration (MRBT) method was used for the determination of the total protein in soya-bean milk. During the process, moving reaction boundary (MRB) was formed by hydroxyl ions in the catholyte and soya-bean milk proteins immobilized in polyacrylamide gel (PAG), and an acid-base indicator was used to denote the boundary motion. The velocity of MRB has a relationship with protein concentration, which was used to obtain a standard curve. By paired t-test, there was no significant difference of the protein content between MRBT and Kjeldahl method at 95% confidence interval. The procedure of MRBT method required about 10 min, and it had linearity in the range of 2.0-14.0 g/L, low limit of detection (0.05 g/L), good precision (RSD of intra-day<1.90% and inter-day<4.39%), and high recoveries (97.41%-99.91%). In addition, non-protein nitrogen (NPN) such as melamine added into the soya-bean milk had weak influence on MRBT results.