摘要
乳酸是三大有机酸之一,其生产主要是生物发酵法和化学合成法。当前,乳酸的生产以生物发酵法为主。发酵生产过程中,乳酸含量的检测是个关键问题。乳酸含量的测定方法较多,其中EDTA定钙法因具有高灵敏性和易操作等优点而得以广泛应用。EDTA定钙法主要是通过钙黄绿素指示剂的黄绿色荧光在滴定前后的有和无进行乳酸测定。但该指示剂变色欠佳,滴定终点难以判断。本研究对EDTA定钙法的指示剂进行改进,即在钙黄绿素指示剂中添加入茜素溶液为衬色剂。改进的指示剂可提高显色反应的对比度,由滴定前的黄绿色荧光变为滴定后的红色,这使终点易于观察和判断,这将提高实验结果的准确度和精密度。实验确定了茜素作为钙黄绿素衬色剂的比例,即钙黄绿素和茜素的较佳混合比例为1∶0.275～1∶0.3(g∶g)。
EDTA titration was a main method for the determination of lactic acid in fermented broth.The color variation of calcein was used to confirm the end point of titration,which is that the original yellow-green fluorescence shifted to the orange color at the end point of EDTA titration.However,the color variation was not sharp,which made some obscurity in confirming the end point of titration.To improve the color variation degree,alizarin was mixed together with calcein in a proportion in this study;and the color variation displayed an obvious shift,which expressed by the fact that the original yellow-green fluorescence was turned into the obvious red color at the end point of titration.The results suggested that the improved indicator made from the mixture of alizarin and calcein was a better indicator,because the color variation of end point was more sensitive;the best proportion of calcein to alizarin was 1：0.275～1：0.3（g：g）.
出处
《食品工业科技》
CAS
CSCD
北大核心
2012年第9期387-389,397,共4页
Science and Technology of Food Industry
基金
国家十二五科技支撑计划项目(2011BAD17B04)
国家海洋局海洋生物活性物质与现代分析技术重点实验室资助(MBSMAT-2010-05)
