Kinetic study of lipid oxidation in roasted coffee

The kinetics of lipid oxidation in ground roast Arabica coffee from Colombia stored under different conditions were studied. Rancidity was controlled by the analysis of the peroxide value at 30-day intervals. The influence of moisture content (26 and 43 g/kg), storage temperature (5, 25 and 35 °C) and packaging conditions (with non-sealed bags, under vacuum, 35 mbar, and packed under CO2 atmosphere) on the kinetics was determined. Experimental values were fitted with a kinetic model for the mechanism of lipid oxidation. Lipid oxidation is described by two steps, which implies a monomolecular and a bimolecular initiation mechanism for the first and second period respectively. The kinetic constants showed that the plastificant effect of water and CO2 lead to an important change in the reactants' mobility within the temperature range. However, the rise in moisture content seems to protect the product from formation of the peroxide. Furthermore, this effect is more important in the second step of the oxidation process.