Factors Affecting the Concentration of Pyrazines in Cocoa Beans

Glc of the pyrazine fraction from roasted cocoa beans yielded nine well resolved peaks which could be quantitated. When beans from several producing countries were roasted under identical conditions, pyrazines generated varied between 142 μg/ 100 g of beans and 698 μg/100 g. The potential for generating pyrazines was greatest in samples from countries where beans are traditionally fermented. Tetramethylpyrazine, trimethylpyrazine, and pyrazines under a peak representing a mixture of 2-ethy1-pyrazine, 2,5-dimethylpyrazine, and 2,6-dimethy1-pyrazine were present in the highest concentrations. In fermented cocoa beans, pyrazine concentration increased rapidly during roasting to a near maximum value which did not change during extended roasting. Results indicate that fermentation influences the rate of formation and final concentration of pyrazines in roasted beans primarily through its effect on the free sugars. Ketoses dominated the sugars fraction (62% of total) in well fermented beans compared to 21% in nonfermented varieties. Tetramethylpyrazine was the only pyrazine detected in unroasted beans and then only in fermented samples.