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Pyrazines and similar nitrogenous chemicals fall, for the most part, into three main odor categories: roasted, peanut or popcorn. They also sometimes display a mixture of these three notes. 5-Methyl-6,7-dihydro-5H-cyclopentapyrazine (FEMA# 3306, CAS# 273747-48-0) is no exception. It combines elements of the roasted and peanut categories with an added hint of an earthy note.
This aroma combination is interesting of itself, but the chemical has a number of other useful attributes. In particular, the aroma combines unusual strength in use with relative heat stability. 5-Methyl-6,7-dihydro- 5H-cyclopentapyrazine first came to the attention of flavorists as a quantitatively significant, and also extremely useful, component of roasted coffee beans, but it has a very wide range of other potential uses. In many flavors it is used in conjunction with other roasted notes, but it always has an important role.
Two other related cyclopentapyrazines also find significant, but perhaps lesser, use in flavors. 2,3-Dimethyl- 6,7-dihydro-5H-cyclopentapyrazine (FEMA# 3917, CAS# 38917-63-4) is slightly weaker than 5-methyl-6,7-dihydro- 5H-cyclopentapyrazine, a little less pungent, but very applicable to nut flavors. 2,5-Dimethyl-6,7-dihydro- 5H-cyclopentapyrazine (FEMA# 4702, CAS# 38917-61-2) has a similar nutty character, perhaps a little more earthy, and works well in peanut flavors. 5-Ethyl-6,7-dihydro-5Hcyclopentapyrazine also has a roasted note, but is overall less interesting.