Thesis (M.Sc.)--Chulalongkorn University, 1996

In this study the stability of aspartame (aspartyl phenylalanine methyl ester) under various pH condition, time and temperature were determined. Study of aspartame degradation chemistry was also included. In order to perform these studies, new analytical method for aspartame-and its degradation products- analysis was also developed. Here, electrospray-mass spectrometry was firstly applied for aspartame analysis quantitatively and qualitatively. The method was optimized to give the best sensitivity of aspartame (detection limit 0.2 ppm) and to simultaneously analyze various degradation products (aspartic acid, aspartyl phenylalanine, diketopiperazine, phenylalanine and phenylalanine methyl ester). The study of aspartame stability under various pH conditions revealed that aspartame degraded into various degradation products via different pathways under different pH conditions. Softdrinks sweetened with aspartame sold in Bangkok were tested and the results showed that the aspartame was partly degraded. If kept for more than 8 months 80% of aspartame was degraded and diketopiperazine was the major degradation products. The result implies the release of methanol upon the degration.