Aspartame - Properties and Use

Properties and Use

Aspartame, an artificial sweetener, is approximately 200 times sweeter than sucrose, or table sugar. Due to this property, even though aspartame produces four kilocalories of energy per gram when metabolized, the quantity of aspartame needed to produce a sweet taste is so small that its caloric contribution is negligible. The taste of aspartame and other artificial sweeteners differs from that of table sugar in the times of onset and how long the sweetness lasts, though aspartame comes closest to sugar's taste profile among approved artificial sweeteners. The sweetness of aspartame lasts longer than sucrose, so it is often blended with other artificial sweeteners such as acesulfame potassium to produce an overall taste more like sugar. Aspartame can be synthesized from its constituent amino acids, -phenylalanine and -aspartate.

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. The stability of aspartame under heating can be improved to some extent by encasing it in fats or in maltodextrin. The 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.

Aspartame's major decomposition products are its cyclic dipeptide (diketopiperazine form), the de-esterified dipeptide (aspartyl-phenylalanine), and its constituent components, phenylalanine, aspartic acid, and methanol. At 180 °C, aspartame undergoes decomposition to form a diketopiperazine (DKP) derivative.

In products such as powdered beverages, the amine in aspartame 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.

Descriptive analyses of solutions containing aspartame report a sweet aftertaste as well as bitter and off-flavour aftertastes.