Abstract:

This study explored the effects of different boiling periods (10, 20 and 30 min) and temperatures (80, 90 and 100 ℃)
for pretreatment as well as different drying temperatures (50, 55, 60 and 65 ℃) and loading weights (16, 24, 32 and 40 kg/m2)
on drying characteristics and length/diameter ratio of betel nuts. The results showed that different boiling periods had no
significant effect on water content, but different boiling temperatures had an obvious effect. The length/diameter ratio of
betel nuts was significantly changed with different boiling periods and boiling temperatures, revealing a decrease with
extended boiling time but an increase with increasing boiling temperature. The optimum pretreatment parameters were
cooking for 10 min at 100 ℃. Both drying time and loading weight had remarkable effects on the moisture content of betel
nuts. The drying rate of betel nuts became higher at elevated drying temperature, but declined with increasing loading
weight. The whole drying process was a falling-rate period. The optimum drying parameters were 60 ℃ and 24 kg/m2 for
drying temperature and loading weight, respectively.

Key words: hot air, drying, betel nut, pretreatment