A group of essential oils that express themselves through an earthy smell and taste of paprika, grass or gooseberries. They are found in many plants and also contribute to the herbal aroma of raw coffee. There are various derivatives of them, such as the two substances IBMP (2-isobutyl-3-methoxypyrazine) and IPMP (2-isopropyl-3-methoxypyrazine). IBMP is one of the most odour-intensive aromatic substances in wine. The odour perception threshold in red wine is only an almost unbelievable 10 to 15 billionths of a gram per litre. This substance is responsible for the paprika aroma (see also under peppery). In contrast, the substance IPMP has a more earthy aroma and is reminiscent of cooked asparagus.
Pyrazine is found in the skin and leaves of certain grape varieties such as Bacchus, Cabernet Franc, Cabernet Sauvignon, Merlot, Sauvignon Blanc, Scheurebe and Sémillon. The proportion is higher in cooler areas and in unripe grapes, and then decreases as the grapes ripen. It can also be increased by vine leaves that have entered the grapes during the harvest. This can happen especially with mechanical harvesting. The taste or smell is usually described as grassy (also herbaceous). Pyrazine aromas are a typical characteristic of bouquet varieties. In Australia, methoxy-dimethylpyrazine has been identified as a cause of cork taint. See a list of all ingredients in wine under total extract.