2-Methoxy-5,6-dimethyl-3- pyrazine acetylation

CIC the earthy odour of fresh potatoes is represented by 2-isopropyl-3-methoxy pyrazine. This earthy note is supported by the mushroom character of l-octen-3-ol. The key component of boiled potatoes is 3-(methylthio)-propanal, balanced with dimethyl sulphide. The high reaction temperatures in baked and fried potatoes start the Maillard reaction to form mainly heterocyclic components 2-ethyl-3,5-dimethyl pyrazine, 2-ethyl-6-vinyl pyrazine, 5-methyl-6,7-dihydro-(5H)cyclopenta-pyrazine, 2-acetyl-l,4,5,6-tetrahydro-pyridine are responsible for the roasted, nutty cracker-like flavour. The heat-induced degradation of the potato lipids and the frying oil imparts a fatty, tallowy character to the french fried potatoes. (E,E)-2,4-Decadienal, 2-octenal, octanoic acid and decanoic acid are main contributors to this fatty note. 

Chlorocarbonyl-2-methoxy-5-methylpyrazine with lithium dimethyl copper reagent in ether gave 3-acetyl-2-methoxy-5-methylpyrazine 2-acetyl-3-methoxy-pyrazine and 2-acetyl-3,6-dimethoxy-5-methylpyrazine were prepared similarly (844), but 2-chlorocarbonyl-3-methoxy-5-methylpyrazine with lithium dimethyl copper in ether gave a mixture of 2-acetyl-3-methoxy-5-methylpyrazine and 2-(l-hydroxy-1-methylethyl)-3-methoxy-5-methylpyrazine (844). 

Wood pyrazine 3-ethyl-2- methoxy- 2-ethoxy- 3,6-dimethyl-3-ethyl- 2-propyl- 2-butyl-3,5- dimethyl- 2-butyl-3,6- dimefhyl- 2- acetyl- 3- methyl- 2-acetyl-3,5- dimethyl- Total... 

Pyrazines are generally associated with nonenzymatic browning. However, pyrazines have also been found as a result of microbial action. Bacillus subtilis was the first organism found to produce a pyrazine (tetramethyl pyrazine [105]). Since that time, several pyrazines (2-acetyl, dimethyl, 2-methoxy-3-ethyl, 2,5 or 2,6-diethyl-3-methyl, trimethyl, tetramethyl, and trimethyl pyrazine) have been identified in aged cheese [16,106-109]. While some of these pyrazines may be formed via the Maillard reaction during aging of the cheese, it is likely that they were formed via microbial action. 

---