Pyrazines coffee flavors

In a recent review on coffee flavor Clarke (3J reported that there are many publications on qualitative data, but information on their actual quantities in coffee is difficult to find. Many of the coffee aroma components are present in high concentrations and these data were used to predict so called consumation ratios for heterocyclic components (7, 9). According to data presented by these authors the consumption of pyrazines from coffee is 380 fold higher compared to pyrazines added as flavoring substances to all other foodstuffs. 

Coffee flavors form during roasting from dicarbonyl compounds which derive from carbohydrates. The thermal degradation of hexoses is thought to be the preciu ors of fin ones like HDMF. The presence of alkylpyrazines affords the characteristic roast notes. These pyrazines are formed through Strecker degradation and the condensation of the resulting Strecker products (60). 

Figure 4.2 shows the distribution according to their functions or structure of the constituents of roasted coffee flavor. Furanic compounds are predominant. The other main constituents are pyrazines, ketones, pyrroles, phenols and hydrocarbons. 

Winter M., Gautschi F., Flament I. and Stoll M. (Firmenich Cie) (1968a) Coffee flavoring containing pyrazines. 

In terms of key aroma components, Czerny et al. [59] conducted sensory studies using volatiles identified in previous studies as potential contributors to coffee aroma [60] to determine the odorants truly characterizing freshly brewed Colombian coffee. They found 2-furfurylthiol, 4-vinylguaiacol, several alkyl pyrazines, furanones, acetaldehyde, propanal, methylpropanal, and 2- and 3-methylbutanal had the greatest impact on the coffee flavor. 

Minuscule quantities of naturally-occurring pyrazines have been found in some foodstuffs and are largely responsible for their flavor and aroma. For example, 3-isopropyl-2-methoxypyrazine is isolated from green peas and wine and a seasoned wine connoisseur can identify a ppt quantity. In addition, 2-methyl-6-vinylpyrazine exists in coffee. 

Pyrazines. In the thirties, the attention on pyrazines was focused on its industrial role in dyes, photographic emulsions and chemotherapy. Its importance in life processes was indicated in its derivative, vitamin B2 (riboflavin, 6,7-dimethyl-9-(l -D-ribityl isoalloxazine). Later,in the midsixties, it was identified in foods and its contributions to the unique flavor and aroma of raw and processed foods attracted the attention of flavor chemists Pyrazine derivatives contribute to the roasting, toasting, nutty, chocolaty, coffee, earthy, caramel, maple-like, bread-like, and bell pepper notes in foods. The reader is referred to the reviews on Krems and Spoerri (88) on the chemistry of pyrazines, and the review of pyrazines in foods by Maga and Sizer (89, 90) Table XVI summaries sensory description and threshold of selected pyrazines. 

Manley et al. (1974) suggested that cyclopentapyrazines may result from the condensation of 2-hydroxy-3-methylcyclopent-2-en-l-one (D.68) with glyoxal or pyruvaldehyde and amino acids, and a mechanism of formation has also been suggested from a study on popcorn flavor by Walradt et al. (1970). Vitzthum and Werkhoff (1975) reported 17 new alkylated five-and six-membered bicyclic pyrazines in roasted coffee the mass spectra of these new constituents and particularly the fragmentation pathways of 2-methyl-(O.50) and of 6,7-dihydro-5-methyl-5//-cyclopentapyrazine (0.51) are discussed in detail. 

Firmenich R., G., R-E and F-H. (Firmenich Cie) (1969a) Pyrazine flavoring agents and flavor modified soluble coffee. Br. Patent 1156484. 

Although pyrolysis of selected leaf constituents generates pyrazines, the diversity and abundance of pyra-zines in smoke cannot be adequately accounted for by this mechanism alone. Maga and Sizer (2439) and Enomoto et al. (17B12) have reviewed the occurrence of pyrazines in roasted foods and proposed pathways for pyrazine formation. Their summaries present a large array of pyrazines found in the flavor fractions of a number of roasted foods. It is striking that nearly all pyrazines commonly found in tobacco smoke have been identified in at least one roasted food. For example, 2,3-dimethylpyrazine has been found in peanuts, barley, coffee, baked potatoes, mushrooms, lamb fat, and tobacco smoke (1587a). 

Pyrazines. Some P. of the types 1-3 are highly active and widely distributed flavor compounds formed either thermally (especially 1 and 2) or biosyn-thetically (3). Alkylpyrazines (1) (see table) have characteristic roast, nut, and potato odors and occur principally in the flavors of coffee, roasted nuts, meat, potatoes, and sea food. 2-Acetylpyrazine (2) has a bread- and popcorn-like odor and is important for... 

More than 100 aroma compounds have been identified in roasted coffee, including such important flavor contributors as furan derivatives, pyrazines, pyrroles, oxazoles, and acids (list AND hOrhammer). ... 

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