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Material study: Heterocyclic Nitrogen- and Sulfur-Containing Aroma Chemicals

By: Michael Zviely (O'Laughlin Industries Ltd.)
Posted: October 25, 2006, from the November 2006 issue of P&F magazine.

In the flavor and fragrance industry, heterocyclic compounds are of interest because of their varied occurrence in food flavors and their valuable organoleptic characteristics. Even though heterocyclic aroma chemicals are found only in minute amounts in foods, their powerful odors and low odor thresholds make them key in boosting flavors and fragrances.

The main heterocyclic aroma chemicals are oxygen-, sulfur- and nitrogen-containing rings. The oxygen-containing heterocyclic aroma chemicals belong to the oxirane, furan, pyran and oxepine groups. The sulfur-containing aroma chemicals belong to the thiophene family and, together with nitrogen, to the thiazole and dithiazine systems. Nitrogen-containing aroma chemicals belong to pyrrole, indole, pyridine, quinoline, pyrazine and quinoxaline systems, and, together with sulfur, as mentioned above, the thiazole and dithiazine families. Here, the nitrogen- and sulfur-containing aroma chemicals are studied.

The nitrogen- and sulfur-containing heterocyclic aroma chemicals can be divided into the following main groups: 

  1. nonaromatic molecules
  2. aromatic molecules

Within the aromatic molecule group, Zviely covers the following: thiophene derivatives, pyrrole and indole derivatives, pyridine and quinoline derivatives, pyrazine and quinoxaline derivatives, thiazole derivatives, alkylthiazoles, acetylthiazoles and hydroxyethylthiazole.

In the last section of this article, Zviely discusses the formation of heterocyclic compounds in food. They are obtained mainly through the Maillard reaction.