2-Acetyl-1-pyrroline

November is flavor and aroma month at MOTW!

2-Acetyl-1-pyrroline (2AP) is a ketone derivative of the heterocyclic compound 1-pyrroline. The hazard information table shows that the pure compound has some dangerous properties, but you probably know it from its pleasing aroma.

In 1982, Ron G. Buttery and Louisa C. Ling at the US Department of Agriculture (Albany, CA) and Bienvenido Juliano at the International Rice Research Institute (Los Baños, Philippines) identified 2AP as an important aroma component of cooked rice. It is present in the volatile oils of basmati and Calrose rice. The researchers also synthesized 2AP via the catalytic reduction of 2-acetylpyrrole, followed by oxidation with silver carbonate.

The following year, the same authors identified 2AP in the leaves of the tropical plant pandan (Pandanus amaryllifolius). The leaves are used as a flavoring agent in south and southeast Asia.

Later in the 1980s, chemists began to identify 2AP in the aroma of baking bread. In 1985, Peter Schieberle and Werner Grosch at what is now the Technical University of Munich (Garching, West Germany) reported that the compound, in addition to other flavor and aroma ingredients, is present in the crusts of wheat and rye breads. 2AP is formed by the Maillard reaction that is characteristic of baking bread, in which amino acids and reducing sugars react to form the components of the crust’s brown color.

Curiously, on a less appealing note, 2AP also contributes to the urine odor of several Asian mammals, including the bintarong (Arctictis binturong; aka the bearcat) and three subspecies of tiger (Panthera tigris).