The effect of cooking and fat content on thermal diffusivity for beefburger-type meat patties while cooking with far infrared radiation was investigated. Most research on thermal diffusivity is based on temperatures below cooking temperatures with the sample in an enclosed container. These conditions do not reflect a commercial cooking practice. An experimental method was designed to determine values for thermal diffusivity in circumstances similar to those in open oven industrial radiant cooking. Temperatures were above pasteurisation temperature and the patties were not enclosed. Evaporation and drip loss could occur freely. Experimental results were examined and found to be reasonable. The initial value of thermal diffusivity for uncooked lean ground beef fell steadily as cooking progressed. From an initial calculated value of 1.94 x 10(-7) m(2) s(-1) the final value was 1.03 x 10(-7) n(2) s(-1). High fat beefburger also experienced a fall, from initial values of around 2.00 x 10(-7) m(2) s(-1) to end values around 1.20 x 10(-7) m(2) s(-1). In keeping with values for thermal diffusivity estimated, the cooking time for fat-added beefburger patties was shorter. This may be attributed to physical changes taking place during cooking. Theoretical analysis is unhelpful in predicting thermal diffusivity under oven-shelf cooking conditions, therefore it is necessary to consider the temperature profile throughout the process. (C) 2002 Elsevier Science Ltd. All rights reserved.