Effect of polyphenol concentration on pyrazine formation during cocoa liquor roasting

A study on effect of polyphenol on pyrazine formation during cocoa liquor roasting has been carried out. Cocoa liquors, having polyphenol concentrations of 41, 58, 116, 143 and 170 g kg−1, were roasted at 120 °C for 15, 25, 35 and 45 min. Results of the study showed that, as polyphenol concentration increases, pyrazine formation decreases; this was due to the binding of polyphenol against pyrazine precursors, i.e. free amino acids and reducing sugars, and pyrazines formed during roasting. Reduction of the formations of 2,3,5-TrMP and 2,3,5,6-TMP occurred throughout roasting times, starting at 116 g polyphenol kg−1 and reaching maximum reduction at 116–170 g polyphenol kg−1. The reduction against 2,5-DMP was not significant over roasting times, except at 35 min; however, formation of 2,3-DMP was reduced at roasting times of 25, 35 and 45 min. These results implied that the presence of polyphenol in cocoa has to be considered in many aspects, including its reduction of flavour formation during roasting, besides productions of astringency and bitterness of the product and its beneficial effect as an antioxidant.