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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/741

Title: Two-stage drying of paddy and the effects on milled rice quality
Authors: Dokurugu, Ibrahim
Issue Date: 10-Aug-2009
Abstract: Two-stage drying of jasmine rice (Oryza sativa L.) cv Khao Dawk Mali 105 and the effects on milling quality was studied. A laboratory fluidised bed dryer was used in the first stage to quickly reduce the initial moisture content of 22.44% wb to ≤19% wb. A second stage of drying using a static bed dryer and sun drying was further carried out until the final moisture content of ≤14% wb was achieved. The experimental drying temperatures at the fluidised bed drying stage were 60°C, 80°C and 100°C. The static bed dryer was adjusted to a tempering temperature of 45°C. The air flow rate at the first stage was set at 2.8 m/s and that of the second stage was 1.3 m/s. The bed depth of the samples at the fluidised dryer was 7cm while the initial mass of each sample was 370g. The experimental data were fitted to the Page’s and Single Exponential drying models to determine which would better describe the data. The Page’s model gave a better description of the data (R2 values as high as 0.966). Drying air temperature had the greatest effect on the rate of drying. Activation energy was calculated as 12.388 × 10-3 kJ/mol and 8.231 × 10-3 kJ/mol for fluidised and fixed bed and fluidised and sun drying respectively. Head rice yield (HRY) of milled rice were 64.22%, 62.11% and 60.36% for fluidised bed drying at 60ºC (first stage drying) static bed drying at 45ºC (second stage drying) and subsequent storage for one, three and six months respectively. The samples dried at 80ºC and 45°C and subsequent storage for same months were 60.22%, 62.20% and 60.51%. Those dried at 100ºC and 45ºC were 59.54%, 62.37% and 57.35%. Complete sun drying had HRY of 62.27%, 63.55% and 61.91%. Those samples which were dried with the fluidised bed dryer and subsequently sun dried and stored for only one month had HRY of 63.29%, 60.06%, 58.37% and 64.25% for drying at 60ºC, 80ºC 100ºC and complete sun drying respectively. It was concluded that drying at 60ºC and storing for one month gave the best HRY for the laboratory dryers whilst complete sun drying had the best HRY at one month storage, though it took an extended time. Head rice yields for the mean drying temperatures and duration of storage were compared; there was no significant difference (p> 0.05) between the mean temperatures and months of storage of dried paddy.
Description: A Thesis submitted to the Department of Agricultural Engineering Kwame Nkrumah University of Science and Technology in partial fulfilment of the requirements for the degree of Master of Science (Food and Postharvest Engineering),2009
URI: http://hdl.handle.net/123456789/741
Appears in Collections:College of Engineering

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