Improved process control by surface temperature-controlled drying on the example of sweet potatoes

Convective drying of food has a big impact on the quality of the product in terms of sensory quality and energy consumption. The temperature of the product during the drying process is a major parameter since exceeding can cause damages to the product. The surface temperature of the product can be measured non-disruptive and contact-free with IR-sensors and this information is used as input parameter for the dryer control. A convective drying chamber was modified with modern sensors and a smart control system to control the surface temperature during the drying process and evaluate the influences on the product in terms of sensory quality parameters like shrinkage, deformation and colour alternation. The dehydration rate in the first drying period of the constant surface temperature-controlled methods is about 1.5 to 2.5 times faster than the conventional method where the air temperature is kept constant and the quality parameters are not significant affected.