Alkyl pyrazines—other than being extracted from various natural sources such as coffee beans, cocoa beans, and vegetables—can be synthesized by chemical methods or by certain microorganisms. The importance of pyrazines for the food industry is expected to grow in the upcoming years due to the higher demand for convenience products. The roasty, nutty, and earthy smell is reminiscent of 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 biotechnological methods have conquered the market recently and are destined to replace the ineffective (0.01% pyrazine kg⁻¹ biomass) extraction from plants or animal sources. This review focuses on the achievements and challenges in pyrazine synthesis. The major part deals with an overview of methods such as the extraction of natural products, the chemical and biocatalytic synthesis, and fermentation by microorganisms. The different types of production are decisive for the declaration and value of the final product and span from 200–3500 US$ kg⁻¹ for the synthetically produced or the naturally extracted 2,5‐dimethylpyrazine, respectively.

中文翻译：

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吡嗪：这些有价值的香料和香精化合物的合成和工业应用

烷基吡嗪不是从各种天然来源（例如咖啡豆，可可豆和蔬菜）中提取的，而是可以通过化学方法或某些微生物合成的。由于对便利产品的需求增加，预计吡嗪类在食品行业中的重要性将在未来几年内增长。烤味，坚果味和泥土味让人想起咖啡和可可，这取决于吡嗪的取代和浓度。人们对日常食物的成分和来源的认识不断提高，对带有“有机”和“天然”等标签的市场产生了强烈影响。通过生物技术方法制备的许多风味成分最近已经占领了市场，并注定要取代无效的（0.01％吡嗪kg ^-1生物质）从植物或动物来源提取。这篇综述着重于吡嗪合成的成就和挑战。主要部分涉及方法的概述，例如天然产物的提取，化学和生物催化合成以及微生物发酵。不同类型的生产对于最终产品的申报和价值具有决定性作用，合成生产的或天然提取的2,5-二甲基吡嗪的价格分别在200-3500美元kg ^-1之间。