Aspartame Degradation in Solution As Impacted by Buffer Type and Concentration

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Aspartame (APM) is a high-intensity sweetening agent incorporated into a variety of diet beverages along with some type of buffer to control the beverage pH. However, data on the effects of individual buffer types and their concentrations on APM degradation rates do not exist. This project evaluated the rate of aspartame degradation in phosphate and citrate buffer solutions at pH 3 and 7 over a concentration range of 0.01-1.0 M ; experiments were performed at 25 °C. APM degradation rate constants were less at pH 3 than at pH 7 as reported previously. The reaction rates increased significantly as buffer concentration increased in both phosphate and citrate buffers. The degradation rate in phosphate buffer was significantly faster than in citrate buffer at pH 7. However, at pH 3, the difference between the rates in citrate and phosphate buffers was diminished. These results suggest that using citrate buffer rather than phosphate buffer would reduce the loss of APM in diet beverages, especially in higher pH beverages. Thus, diet beverages formulated with citrate buffer would have longer shelf lives than those formulated with phosphate buffer. In addition, this study provides general insight as to the mechanisms by which buffers may destabilize food ingredients.