Changes in free radicals content in coffee beans throughout convective roasting and microwaving and during storage

Coffee beans were analysed for free radicals by ESR spectroscopy. Effects of roasting method (convective roasting or microwaving) and initial beans' moisture (5-10%) on free radicals generation and changes in their content during 6 months storage of ground and vacuum-packed material were determined. ESR spectroscopy studies revealed that concentration of free radicals in roasted beans was only slightly affected by roasting method and was mainly dependent on the initial beans' moisture, which also had a strong impact on overall roasting process. When coffee beans were less humid prior to thermal processing, synthesis of free radicals was more intensive throughout roasting and was continued for a longer time during storage of roasted material.