Over supply of fresh longan (Dimocarpus longan Lour.) from seasonal
production in Thailand needs to be preserved to prevent it
from being damaged by microorganisms. Among the preserved
products, dried longan is one of the important products with an export
value of more than US$70 million in 2009 (Office of Agricultural
Economics, 2009). A common industrial process used to dry
peeled and unpeeled longan is hot air drying using solar or lique-
fied petroleum gas (LPG) as the energy source. This technique is
convenient, but its disadvantages are long drying time, low energy
efficiency and inferior quality of dried products.