The kinetics of polyphenol degradation during the drying of Malaysian cocoa beans

Abstract The main objective of the study was to determine the kinetics of the polyphenol oxidation reaction in cocoa beans during air drying at various air temperatures and humidities. The temperatures used were between 40 and 60 °C and the relative humidities were between 50 and 80%. The higher the temperature and relative humidity of the drying air, the lower the amount of polyphenol residue in the cocoa beans, because of enzymatic oxidation of polyphenols. At higher drying temperatures, non-enzymatic oxidation of polyphenols could also occur. Computer simulation results gave rate constants for the polyphenol oxidation reaction (k1) and the condensation reaction (k2), at various air conditions, in the range of 0.055–0.200 and 0.136–0.155 h−1 respectively. The activation energies obtained for the polyphenol oxidation reaction were in the range of 27 800–30 312 J K−1 mol−1. The reaction kinetics of the enzymatic browning reaction fitted a pseudo first-order reaction.