While aspartame, like other peptides, has a caloric value of 4 kilocalories (17 kilojoules) per gram, the quantity of aspartame needed to produce a sweet taste is so small that its caloric contribution is negligible, which
makes it a popular sweetener for those trying to avoid calories from sugar. The taste of aspartame is not identical to that of sugar: aspartame’s sweetness has a slower onset and longer duration than sugar’s, and some consumers find it unappealing.
Blends of aspartame with acesulfame potassium are purported to have a more sugar-like taste, and to be more potent than either sweetener used alone.
Like many other peptides, aspartame may hydrolyze (break down) into its constituent amino acids under conditions of elevated temperature or high pH.
This makes aspartame undesirable as a baking sweetener, and prone to degradation in products hosting a high-pH, as
required for a long shelf life. Aspartame’s stability under heating can be improved to some extent by encasing it in fats or in maltodextrin. Aspartame’s stability when dissolved in water depends markedly on pH. At room temperature, it is most stable at pH 4.3, where its half-life is nearly 300 days. At pH 7, however, its half-life is only a few days. Most soft-drinks have a pH between 3 and 5, where aspartame is reasonably stable.
In products that may require a longer shelf life, such as syrups for fountain beverages, aspartame is sometimes blended with a more stable sweetener, such as saccharin.
In products such as powdered beverages, aspartame’s amino group can undergo a Maillard reaction with the aldehyde groups present in certain aroma compounds. The ensuing loss of both flavor and sweetness can be prevented by protecting the aldehyde as an acetal.
