Pyrazines, food flavour

Several mechanisms have been proposed for the formation of pyrazines in food flavours [18, 23, 25], but the major route is from a-aminoketones, which are products of the condensation of a dicarbonyl with an amino compound via Strecker degradation (Scheme 12.3). Self-condensation of the aminoketones, or condensation with other aminoketones, affords a dihydropyrazine that is oxidised to the pyrazine. 

Other fused heterocycles have very attractive flavour and odour properties. Pyrazines, in general, are important in many strong food flavours a fused pyrazine with a ring junction nitrogen atom is one of the most important components in the smell of roast meat. You can read about the simple pyrazine that provides green peppers with their flavour in the Box on the next page. 

Maga J.A. (1982b) Pyrazines in flavour. In Food Flavours. Part A. Introduction. Morton I.D. and McLeod A.J., Eds, Elsevier Scientific Publishers, 283-323. 

Maga, J.A., Pyrazines in flavor, in Food Flavours, Part A. Introduction, I.D. Morton, A.J. MacLeod, Eds., Elsevier Scientific Publ., Amsterdam, 1982, p. 283... 

As for S-containing heterocycles, many N-containing heterocycles are also found in heat-treated foods as secondary flavours as a result of Maillard-type reactions between reducing sugars and amino acids. Pyrazines are N-heterocycles important contributors to the taste and aroma of roasted and toasted foods as well as vegetables and fermented foodstuffs. In cultures of Pseudomonas perolens ATCC 10757, amino acids such as valine, glycine and methionine were shown to... 

Chemists produce synthetic flavourings such as smoky bacon and even chocolate . Meaty flavours come from simple heterocycles such as alkyl pyrazines (present in coffee as well as roast meat) and furonol, originally found in pineapples. Compounds such as corylone and maltol give caramel and meaty flavours. Mixtures of these and other synthetic compounds can be tuned to taste like many roasted foods from fresh bread to coffee and barbecued meat. 

Hawksworth, G. Scheline, R.R. (1975) Metabolism in the rat of some pyrazine derivatives having flavour importance in foods. Xenobiotica 5, 389-399. 

Maga JA (1982) Pyrazines in foods an update. CRC Grit Rev Food Sci Nutr 16 1-48 Maga JA (1989) Sensory and stability properties of added methoxypyrazines to model and authentic wines. In Charalambous G (ed) Flavors and off-flavors, proceedings of the 6th international flavour conference, Rethymnon, Crete, Greece, 5-7 Jiily 1989. Elsevier, Amsterdam, pp 61-70... 

Descriptive terminologies for the odours of pyridines use terms such as green, bitter, astringent, roasted, burnt, pungent, solvent and fishy, none of which could be considered desirable. Their presence in some food commodities, such as beer and whisky, is disagreeable and associated with a cardboard, oxidised and harsh flavour. In roasted coffee, pyridines may contribute to a pleasant smell that is, however, less pleasant than the smell of pyrazines. 

Many pyrazines are synthesised and used to flavour foods, such as instant coffee, ice creams, potato products and many... 

In the second pathway, dehydration of 3-deoxyhexosones leads to hydroxymethyl furaldehydes. The reactions which follow the formation of these intermediates are complex and result finally in the formation of dark brown nitrogen-containing pigments and also N-heterocyclic compounds such as pyrazines and pyrroles, which appear to be mainly responsible for the roasted, bready and nutty flavours of heated foods. 

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