Quality analysis of microwave dried iron yam chips controlled by infrared thermal imaging

Abstract

The aim was to study the real-time temperature control by infrared thermography and the quality changes of the iron yam chips during drying processes. Microwave (MW) and heat pump (HP) were used to dry iron yam chips at 50, 60 and 70 °C. The material surface temperatures were online controlled by infrared thermal imaging system in the process of microwave drying. Temperature, drying efficiency, texture and color were estimated. The experimental results were shown on the basis of drying process characteristics and dried product qualities. Temperature fluctuations became more violent with the increase of drying time and drying temperature, and had a negative impact on the quality of dried iron yam chips. There were no significant differences of hardness and cohesiveness between both drying methods. The springiness and chewiness values of iron yams dried by HP were lower than samples dried by MW. It is worth noting that lightness and white index values of the iron yam chips dried by microwave at 70°C were obviously lower (p < 0.05) than the fresh samples and the iron yam chips dried by heat pump.