Abstract: In this paper, the heat transfer during mutton roasting using an electric tube heater coupled with infrared radiation was analyzed in order to the optimal processing parameters for the quality characteristics of “scorched outside but tender inside”. During the roasting process, the temperature distribution was measured by infrared imaging technology, and the relationship between internal temperature and roasting temperature and time was analyzed based on thermodynamic parameters and three-dimensional unsteady heat conduction model. Water loss and protein denaturation were examined by a differential scanning calorimeter. The effect of infrared radiation power on roast mutton quality was evaluated as well as the effect of smearing oil on the surface of meat on heat conduction. Results showed that the roasting process could be divided to two stages. The first stage lasted for 5 min at 85–140 ℃, where the heat was transferred from the exterior to the interior, facilitating the development of aroma and flavor substances, and heating was stopped when the internal temperature reached 60 ℃ followed by smearing oil on the meat surface and cooling. At the second stage, a 2.0 kW shortwave infrared tube heater was used to heat for 2 min, quickly increasing the surface temperature to 120 ℃; the Maillard reaction was more complete due to the high heat flux and low penetrability of shortwave infrared radiation, leading to the generation of coking film barrier layer, reduced water loss from the meat interior and increased temperature difference between the surface and interior of mutton. Finally, the quality characteristics of “scorched outside but tender inside” could be achieved through accurate control of roasting temperature, time and method, which together with understanding the underlying thermodynamic mechanism may provide a basis for the research and development of industrial meat roasters.

Key words: natural convection, infrared radiation, roasting, heat transfer