Turmeric drying using a combined vacuum and far-infrared dryer

Abstract

Turmeric (Curcuma Longa Linn.) is the herb that has been widely used in the modern and traditional medicine. However, the utilization of fresh turmeric is limited because it was easy deterioration. Since, the drying process was applied to preserve the turmeric. The aim of this research was to investigate the drying kinetics and qualities of turmeric using a combined vacuum and far-infrared drying. The experiments were carried out at the following conditions: absolute pressure of 2 and 5 kPa; controlled drying temperature at turmeric surface at 50, 60 and 70 degree Celsius. In drying process, the samples were dried until reaching the final moisture content of 5 %(d.b.) Based on this experiment the drying kinetics depends on the slice thickness, absolute pressure and drying temperature. For color change, the lightness and yellowness increased with an increase in drying temperature while the redness was quite constant. Furthermore, the curcumin content of the dried turmeric was higher than that of Thai industrial Standards Institute.