Abstract:
This research aims to develop dried Nam Dok Mai mango products using Far-Infrared combined with hot air (FIR+HA) at constant temperature and temperature-reducing mode compared to hot air (HA) drying. The drying kinetics, specific energy consumption of the drying process, and quality of dried mangoes were evaluated. Mangoes with a total soluble solids content of 1819 °Brix were sliced to a thickness of 1.5 cm and dried using infrared combined with hot air at a power of 650 W and hot air at a temperature of 7090 °C. This was compared to infrared drying combined with hot air with temperature reduction at a power of 650 W, hot air at a temperature of 90 °C and 100 °C for 1-2 hours, and hot air drying at 70 °C. All three methods were dried until the samples had a moisture content of no more than 15% dry basis. The results showed that the infrared drying method combined with hot air at 90 °C had a higher drying rate than other drying methods, resulting in a shorter drying time and lower specific electrical energy consumption than other drying methods. Mangoes dried with infrared combined with hot air at 90 °C had lower lightness (L*), shrinkage percentage, hardness, and elasticity, but higher redness (+a*) and yellowness (+b*) values, and a larger porous structure than other drying conditions. Meanwhile, mangoes dried with infrared combined with hot air at a temperature reduction of 90 °C for 1 hour had the highest lightness and yellowness values, but the lowest redness value. Increasing the temperature and drying time in the first step of the drying process resulted in lower lightness, yellowness, hardness, toughness, and shrinkage percentages, but higher redness and larger pore size. The recommended conditions for drying mangoes are drying with infrared combined with hot air at a temperature reduction of 90 °C for 1 hour, followed by 80 °C for 1 hour, and 70 °C for 1 hour.