Effect of roasting conditions and grinding on free radical contents of coffee beans stored in air

The influence of roasting and storage conditions on free radical contents of individual Arabica coffee beans was examined during storage of whole, half and ground beans in air over a 1-month period. Free radical contents increased with increasing roasting time (roasting degree), but the atmosphere (air vs. N 2 ) used in the roasting and cooling process had little effect. There was a progressive increase in free radical contents with storage time, but the rate was much lower in whole beans than with half and fully ground beans, for which the rate was similar. These results suggest that exposure to O 2 , rather than physical grinding is the main mechanism for storage-related free radical generation, and strongly indicate that roasted coffee is best kept as whole beans in order to minimise changes during prolonged periods of aerobic storage. Furthermore, they demonstrate that EPR measurements can contribute to understanding the process and storage related changes in coffee.