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