Generally, aspartame can be commercially produced from the chemical reaction among L-aspartic acid, L-phenylalanine and methanol. There are several synthesis methods that can be used. The following are the four brief manufacturing processes that came up by the China manufacturer – Yamei (1), who closed in 2017.

Anhydride reaction (Step 1): the reaction among formic acid, acetic anhydride, and L-aspartic acid to obtain N-formyl-α-L-aspartic anhydride.

Condensation (Step 2): then react N-formyl-α-L-aspartic anhydride with L-phenylalanine and sodium hydroxide to produce N-formyl-a-L-aspartyl-L-phenylalanine.

Esterification (Step 3): then react with methanol and hydrochloric acid to obtain α -L-aspartyl-L-phenylalanine methyl ester hydrochloride.

Neutralization (Step 4): then neutralize with Na2CO3 to produce N-L-alpha-Aspartyl-L-phenylalanine-1-methyl ester (aspartame).

Property
Other names    N-L-alpha-Aspartyl-L-phenylalanine-1-methyl ester, Aspartyl phenylalanine methyl ester, APM
CAS number    22839-47-0
Chemical formula    C14H18N2O5
Molecular weight    294.31
PH    0.8% solution is between 4.5 and 6.0
Solubility    sparingly soluble in water (approximately 10 g/L at room temperature), and slightly soluble in alcohol (0.37 % in ethanol and insoluble in oil)
Appearance
A white, crystalline powder or granular.

Taste
With a sweet taste of pure, refreshing and strong, approximately 200 times as sweet as sucrose, and the taste is very similar to it. Without the bitter, chemical or metallic aftertaste often found in other artificial sweeteners.

Synergy
Synergistic with other sweeteners. For example, when aspartame and acesulfame potassium are mixed with the ratio of 1:1, the sweetness can reach to 300 times sweet than sucrose, while both the sweetness is 200 times if used alone.

Which means the desired sweetness can be obtained with less amount of sweeteners. Meanwhile, aspartame can mask the bitter and astringent taste of other sweeteners such as sodium saccharin.

A further benefit of synergy is to reduce the instability of aspartame in soft drinks. When aspartame is mixed with another more stable sweetener, the shelf life of soft drinks can be extended.

Structure
Unlike other artificial sweeteners, the structure of this ingredient is made of two amino acids (l-aspartic acid and l-phenylalanine), and also with methanol. It can be metabolized and absorbed in the body like protein.
 

The functional groups are carboxyl, ester, primary amine, amide, and phenyl.