Aspartame

Aspartame is a high intensity sweetener that is a dipeptide, providing four calorie per gram. It is synthesized by combining the methyl ester of phenylalanine with aspartic acid, forming the compound N-L-alpha-aspartyl-L-phenylalanine-1-methyl ester. It is approximately 200 times as sweet as sucrose and tastes similar to sugar.

It is comparatively sweeter at low usage levels and at room temperature. Its minimum solubility is at pH 5.2, its isoelectric point. Its maximum solubility is at pH 2.2. It has solubility of 1 per cent in water at 25 centigrade. The solubility increases with temperatures. Aspartame has a certain instability in liquid systems which results in a decrease in sweetness. It decomposes to aspartylphenylalanine or to diketropiperazine (DKP) and neither of these forms is sweet.

The stability of aspartame is a function of time, temperature, pH, and water activity. Maximum stability is at approximately pH 4.3, and it is not usually used in baked goods as it breaks down a the high baking temperatures. It contains phenylalanine, which restricts its use for those afflicted with phenylketonuria, the inability to metabolize phenylalanine. Uses include cold breakfast cereals, desserts, topping mixes, chewing gum, beverages, and frozen desserts. The usage level ranges from 0.01 to 0.02 per cent.

Source: Dictionary of Food Ingredients (Robert S. Igoe)