The objective of this research was to investigate suitable condition for drying kaffir lime leaves
mulberry leaves and pineapple with heat pump and combined heat pump and infrared (300W) at
temperature of 45, 55 and 65?C. The changes of physical properties including moisture content, water
activity, rehydration ratio, color and chemical properties including ?-carotene in kaffir lime leaves,
flavonoid in mulberry leaves and vitamin C in pineapple, total phenolic content and antioxidant activity
in all samples were determined. The results showed that the moisture content and drying time to reach
the final moisture content below 12%wb for kaffir lime leaves, 10%wb for mulberry leaves 18%wb for
pineapple and 14%wb for paddy rice decreased with higher drying temperature. Water activity of dried
samples were less than 0.6 for all dried samples. Moreover, drying temperatures did not give significant
effects on total color difference value and rehydration ratio of dried samples. Overall, our findings
suggest that drying of kaffir lime leaves, mulberry leaves pineapple and paddy rice with combined heat
pump and infrared system at 65?C for 120, 60 180 and 480 min are the best condition, respectively.