Non enzymatic browning during cocoa roasting as affected by processing time and temperature

Non enzymatic browning (NEB) kinetics were studied at 125, 135 and 145 °C during a cocoa beans roasting process aimed to reach a final moisture content of 2 g 100 g-1. Colour lightness and hue angle decreased with roasting time following a first and a zero order kinetic, respectively. Moisture content being equal, high temperature-short time (HTST) roasting processes minimized the extent of browning reaction. Melanoidins increased with roasting time following an asymptotic kinetic. Moisture content being equal, HTST processes maximized the melanoidins formation. The energy of activation of melanoidin formation (132 kJ mol-1) was higher than those of colour changes and polyphenol oxidation (between 60 and 80 kJ mol-1), thus NEB during roasting is not solely dependent on Maillard reaction occurrence. Hydroxymethylfurfural (HMF) increased exponentially with roasting time but its final content was low (0.1-0.8 g kg-1). HTST processes minimized the HMF formation, which was not temperature dependent and was influenced by concentration.