In this study, the effect of the cooking time and temperature on the dimensions and crease of the wheat kernel was studied during bulgur production. Wheat was cooked at 87, 92 and 97 degreesC for 140 min. The change of the length, two widths, weight, volume and density for the wheat kernel were determined during the cooking operation. In addition, in order to determine the effect of cooking time and temperature, rates, activation energy, Q(10) and z-values were determined. Negative percent change values and the rate constant for the length and density of the wheat kernel were obtained at different cooking temperature (P > 0.05). A positive rate constant was determined for other properties. The crease side width increased gradually at each cooking temperature between 6.95-68.05%. Cooking time also significantly affected the change of the crease side (P < 0.05). The secondary width was affected significantly (P < 0.05) by the cooking temperature and time, and its value changed between 9.95-69.00%. The big change for the secondary width was obtained at 97 degreesC. The crease has important guarding property for the length and secondary width and it also guards the kernel for the secondary width against the internal force up to 97 degreesC. The volume of the kernel also increased (27.35-185.20%) during the cooking operation significantly (P > 0.05), and has greater percent change value than the weight (19.25-160.70%) due to high amount of swelling of the wheat kernel. Therefore, density changed negatively. E-a, Q10 and z-values were determined for all physical properties of the wheat kernel and found that cooking temperature significantly, affected the change of the c, W and p values. (C) 2003 Elsevier Ltd. All rights reserved.