Determination of the Sweetener Aspartame with an Enzyme Sensor

SHU-FEN CHOU, JIAN-HUA CHEN, LONG-WU CHOU, JIN-JIA FAN, *CHIEN-YUAN CHEN

Department of Food Health, Chia-Nun College of Pharmacy, Tainan Hsien, Taiwan, R.O.C.
*Department of Agricultural Chemistry, National Taiwan Univevsily, Taipei, Taiwan, R.O.C.

ABSTRACT

   This study attempted to establish an efficient, convenient enzyme sensor for the determination of aspartame in foodstuff. The sensor system we investigated was a bienzyme system composed of a-chymotrypsin and alcohol oxidase, immobilized by an entrapping method with dialysis membrane, subsequently combined with the dissolved oxygen electrode equipment. This method was able to determine aspartame efficiently. The optimum operational conditions for the enzyme sensor were pH 6.5--8.5 and 30 ???. A linear relationship was observed between D.O. decrease and the aspartame concentrations in the range of 0.1-2 mM. One assay could be completed within 10 minutes. When the enzyme electrode was stored in dithiothreitol solution, the system was stable for more than 7 days and 70 assays. When this system was used for the determination of aspartame in commercial non-alcoholic products, the results were found to be in close agreement with the labelled values provided by manufacturer (within 5% of the relative error).

Key words : Enzyme sensor, entrapping method, α-chymotrypsin, alcohol oxidase, aspartame