Effects of roasting on alkylpyrazin compounds and properties of cocoa powder.

The volatile flavor compounds are the most important indicators of the quality of cocoa beans, among which pyrazines are considered as the main and key groups affecting the cocoa flavor. In cocoa processing, roasting is an important stage in the technical treatment of cocoa and has a significant impact on chemical properties of cocoa and its flavor. The present study aimed to assess the impact of roasting (temperature and time) on alkyl pyrazines, as key flavor compounds, via gas chromatography-mass spectrometry. Additionally, other properties, including color, polyphenols, chemical properties, and sensory attributes of cocoa powder were investigated. The results indicated that with the change in roasting time and temperature, these properties changed significantly. The cocoa powder roasted at 140 °C for 40 min had the highest browning index value (OD(460)/OD(525)), tetramethylpyrazine to trimethylpyrazine (TMP/TrMP) ratio, and sensory evaluation score and the lowest polyphenol content compared to the other samples.