Production of dried fruit and vegetables using specially-designed dryer
1991
Bulan Phithakpol | Warunee Varanyanond | Maradee Phongpipatpong (Kasetsart Univ., Bangkok (Thailand). Inst. of Food Research and Product Development)
Drying system was designed and constructed by Department of Mechanical Enginerring, Kasetsart University, The dryer was constructed by circulating hot air from the bottom to the top of the dryer. The temperature distribution was studied at 50-60 deg C by using both LPG and rice husk as sources of energy. The temperature variation inside the dryer was 5-10 deg C. The average LPG consumption was 2.38 kg/hr and rice husk was 11-12 kg/hr. The cost of LPG was 5 times of the rice husk, therefore rice husk was used as an energy source for drying trials. The hot air circulation system and rice husk feeding system with temperature control were improved. Hot air circulation from the top to the bottom of the dryer was found to give more even temperature. Drying trials with bananas and red chillis were conducted. Bananas with average moisture content of 68.68 % and 20 deg Brix were dried for 18 hours at 60-70 deg C and 67-78 % RH with 18 % final moisture content. Fresh red chilli pretreated by steaming and blanching was dried at 60-70 deg C with hot air, RH of 10-30 %, in 14 hours. Unblanched and blanched dried red chilli gave similar results with the moisture content of 12 %. The design of this drying system was suitable for agricultural waste, as rice husk rather than LPG.
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