Pyrazines – valuable flavour & fragrance compounds: Biocatalytic synthesis and industrial applications.

Substituted alkyl pyrazines - other than being extracted from various natural sources such as coffee beans, cocoa beans, nuts and vegetables - can be synthesized by the use of traditional chemical methods or by the help of certain microorganisms. The importance of pyrazines for food industry is expected to grow in the upcoming years due to the higher demand for ready meals, coffee and chocolate drinks; the roasty, nutty and earthy smell is reminiscent for coffee and cocoa depending on substitution and concentration of pyrazines. The growing awareness of people about the ingredients and the origin of their daily food has strongly influenced the market with labels like ’organic‘ and ’natural‘. Many flavor ingredients prepared by biotechnology methods have conquered the market in recent years and are destined to replace and optimize the ineffective (0.01% pyrazine/kg biomass) extraction from plants or animal sources. This overview focuses on the achievements and the upcoming challenges in pyrazine synthesis. Major parts deal with the extraction of natural products from sugar molasses, the chemical synthesis, fermentation by microorganisms and preparative methods by biocatalysis. The different types of production are decisive for the declaration and value of the final product and can span from 200-3500 $/kg for the synthetically produced or the naturally extracted 2,5-dimethylpyrazine, respectively.