Hazelnut roasting was analyzed using response surface methodology to find out the effect of process variables on color development during roasting and to establish prediction models. The roasting temperature was found to be the main factor affecting color development. Developed prediction models satisfactorily described color development as a function of roasting temperature and exposure time for L-value, a-value and b-value of whole-kernel, ground-state and cut-kernel measurements. Whole-kernel measurements were significantly lighter in color compared to ground-state and cut-kernel measurements due to internal browning of the hazelnuts during roasting. The results also indicated that the L-value of ground-state measurements, which take into account internal browning during roasting, should be used to monitor roasting of hazelnuts. (C) 2000 Elsevier Science Ltd. All rights reserved.