Determination of aspartame degradation kinetics in diet sour cherry syrup using HPLC

Due to obesity disorders and related diseases, low calorie soft drinks have been greatly favored in recent years. In this study, all the sugar in the reference syrup was eliminated to produce diet syrups. Pectin as a bulking agent and aspartame and acesulfame-k as sweeteners substitute for sucrose were applied. For studying the selected formulations during storage, these syrups were stored at room temperature and 40 °C for 4 months. Degradation of aspartame was measured using HPLC method and then its degradation kinetics was determined. Results showed that time and temperature had significant effects (p<0.001) on the aspartame stability but the type of formulation (different types of syrups) had no significant effects. The first order reaction rate was applied for calculating the constant rates of aspartame degradation. The calculated reaction rate constants for the diet syrups were about 0.1 at ambient temperature and about 0.3 at 40 °C. The half-life of the aspartame degradation was about 4 months at ambient temperature and about 2 months at 40 °C. Therefore, the amount of aspartame in the product depends on temperature, time and environmental conditions. Acceptability of aspartame decreases at high temperatures due to the degradation of aspartame, so it is not suggested to be used in sour cherry syrup in these conditions. But, it can be easily used in sour cherry syrup at around ambient temperatures.