市販飲料のビタミンC含有量とその分析法について

抄録

We determined the amount of ascorbic acid (AsA) in 31 commercial non-alcoholic beverages sold in Osaka City, Japan. AsA was analyzed by high performance liquid chromatography (HPLC) using a LiCrosorb 100 NH₂ column and 3mM ammonium phosphate/acetonitrile (30:70) as mobile phase. Concentrated-restored fruit juices contained 210-470μg/ml AsA, more than natural fruit juices (110-140μg/ml). The content of AsA in tea drinks was similar to that in concentrated-restored fruit juices at 290-360μg/ml. Furthermore, beverages prepared from natural materials such as orange juices or green tea showed differing AsA content between different product lots.
To estimate the difference between AsA analytical methods, we used 5 AsA analytical methods, HPLC, the indophenol titrimetric method, the dinitrophenylhydrazine method, the fluorometric method, and the enzymic method. In green tea, the enzymic method showed the minimum reading, which was 80% of that found using the indophenol titrimetric method, which showed the maximum. The AsA content of concentrated-restored fruit juices varied widely according to method. The dinitrophenylhydrazine and enzymic methods showed significant difference from other methods; in particular, the enzymic method showed 1.8-2.9 -fold higher AsA content than HPLC. The AsA content of natural fruit juices showed no appreciable difference between methods. These findings suggest that the enzymic method cannot determine accurately the AsA content of concentrated-restored fruit juices. Whether a fruit juice is concentrated-restored or natural can probably be distinguished by the difference in AsA content using the enzymic and HPLC methods.