Isopropyl-2-methoxypyrazine, 3-, potato aroma

Three extremely odorous pyrazines, 3-isopropyl-2-methoxypyrazine, 2-s-butyl-3-methoxypyrazine, and 2-isobutyl-3-methoxypyrazine have been shown to be present in green peas, and are likely to be of major significance in the flavor of peas (59). The volatile oil of green bell peppers has been found to contain 2-isobutyl-3-methoxypyrazine as a major component (60,61). The alkylpyrazines in potato chips (62,63) and roasted peanuts (63) have been examined. 2-Isopropyl-3-methoxypyrazine has been characterized in the vacuum steam volatile oil of potatoes (64), 2-ethyl-3-methoxypyrazine in cooked potato (65), and 3-ethyl-2,5-dimethylpyrazine and 2-ethyl-3,5-dimethylpyTazine as the components important to the aroma of baked potato (66). A variety of alkylpyrazines have been identified in roasted sesame seeds (67) and 21 pyrazines have been identified in the aroma components isolated from roasted green tea (68). 

Ethylmethoxypyrazine. Unlike the isobutyl-, isopropyl- and sec-butyl methoxypyrazines, the existence of 2-ethyl-3-methoxypyrazine (4) (ethylmethoxypyrazine) in fruits and vegetables has not been consistently confirmed in the past. While evidence for its existence was found, unambiguous identification by mass spectrometry was prevented by the trace concentration of this component. Of all the methoxypyrazines so far mentioned, it has an aroma most similar to raw potatoes 16) and synthetic material adds potato flavor to processed potato products (18). It is also described as earthy 15), and it has a sensory detection threshold of 425 ng/L (17). Given its aroma, it is not surprising that its possible occurrence in potatoes has been the subject of several studies. 

Isopropyl-3-methoxypyrazine and 2,5-dimethylpyrazine, with their typical earthy flavour, have great importance for the aroma of rawpotatoes (Solanum tuberosum, Solanaceae). In addition to these compounds, raw potatoes contain a range of carbonyl compounds and alcohols. A very important component of the aroma of cooked potatoes is methional. 

Despite their overall high abundance, the sesquiterpene hydrocarbons ( )-caryophyllene and )S-elemene were not detected by GCO and AEDA. This indicates that these compounds may play either no role or only a minor role in the overall aroma of O. sanctum. Results of AEDA (Table 1) indicate that eugenol cloves) is the predominant odorant in the essential oil, followed by jS-damascenone (floral, applesauce), 2-isopropyl-3-methoxypyr-azine (earthy, potato), and 1,8-cineol (minty, eucalyptus). The fact that eugenol and 1,8-cineol are key aroma components is not surprising and is supported by previous studies [1-9]. However, jS-damascenone and 2-isopropyl-3-methoxypyrazine had not been previously reported as components of O. sanctum. The AEDA procedure was conducted on the fresh herb to determine whether these latter components are indeed natural constituents of the herb or whether they are generated during the production of the... 

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