2.1.2. Infrared cooking procedure
Ohmically pre-cooked meatball samples were directly transferred to the infrared cooking device which was already combined to the ohmic cooking unit (Fig. 1b). The infrared cooking unit was designed to involve a specially rotating belt with motor for controlling speed, a power supply controlled with closed-circuit microprocessor unit and a heating cabinet (Fig. 1c). The detailed information about the infrared cooking procedure was put forth by Kendirci et al. (2014). The infrared heating cabinet consisted of specially polished reflective stainless steel inside walls, infrared heating source (4 μm wavelength, Philips) and temperature measurement units. (T-type thermocouples). The application heat fluxes could have been adjusted in the range of 3–10 kW/m2. Cylindrical meatball was placed longitudinally into the continuous belt of the infrared system. The application distance between the infrared source and the meatball surface could have been adjusted in the range of 10–16.5 cm (Fig. 1c). The speed of the belt of the infrared unit was adjusted to obtain the prescribed residence times (4, 8 and 12 min) of the meatballs in the infrared unit. Since the infrared radiated directly the upper lateral surface of the meatball, samples were turned over to radiate the other surface for the half application time of the process. Infrared cooking parameters were selected as three different heat fluxes (3.706, 5.678 and 8.475 kW/m2), three different application distances (distance between infrared unit and surface of meatball; 10.5, 13.5 and 16.5 cm) and three different application durations (4, 8 and 12 min).