Fundamental drying phenomenan of cut welsh onion by an infrared heater combined vacuum operation and convection
Sunate Mongpraneet; Takemi Abe and Takashi Tsurusaki
Proceedings of the APEC symposium on postharvest handling systems Bangkok, Thailand September 1-3, 2003. p. 183
2003
บทคัดย่อ
Fundamental drying phenomenan of cut welsh onion by an infrared heater combined vacuum operation and convection
A comparative study of the effects of initial power supply on the drying of the leafy part of welsh onion by a far infrared heater under reduced pressure and convection were studied to understand the drying phenomenon. The drying rate as a function of moisture content was studied vis-à-vis drying qualities such as rehydration potential, shrinkage, and color change. The three characteristic pre-heating, constant, and falling rate periods were obtained in both drying techniques. Drying rate increased with increasing radiative energy input and was higher under the reduced pressure environment than in the convective condition as was shrinkage and rehydration ratio. For optimum drying speed and product quality vis-à-vis energy savings in the drying of welsh onion, it was recommended that FIR-vacuum operation at 70-watt initial power supply Z0.17-W/cm2 radiation intensity) be used.