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Thin Layer Drying of Hybrid Rice Seed

Prof. Dr. B.K. Bala
Supervisor
Department of Farm Power and Machinery, BAU, Mymensingh

Prof. Dr. Md. Burhan Uddin
Co-supervisor and Chairman, Examination Committee and Head
Department of Farm Power and Machinery, BAU, Mymensingh

Abstract/ Executive Summary:

This study presents thin layer drying of hybrid rice seed to assess the effects of drying air temperature on drying performance and quality of the dried rice seed in terms of germination capacity and colour. Thin layer drying apparatus was used to dry the seed from 22% (wb) to equilibrium moisture content at 40º C, 50º C and 60º C respectively. Time required for 40º C, 50º C and 60º C were 540 minutes, 250 minutes and 200 minutes respectively. It was found that drying temperature had significant effects on the seed germination capacity. Germination percentage was highest at 400 C drying air temperatures. In this work thin-layer drying models were developed. The results showed that the Midilli 47 et al. achieved the highest rank, the two term exponential ranked second for different temperatures followed by the Page, Henderson and Pabis and Newton model. The agreement between the predicted and experimental results for these three temperatures (400 C, 500 C and 600 C) was excellent. Here, the highest R2 (close to 1) and the lowest RMSE values indicate the highest grade point and highest average grade point ranked first. Colour of paddy did not change with the change of drying temperature. Lightness, hue angle and chroma were determined and found almost similar for three different drying temperatures.

Keywords: Drying temperature, Rice seed, Germination percentage, Paddy seed, Temperatures, Quality of seed

Location: Department of Farm Power and Machinery, BAU, Mymensingh, Bangladesh

Start Date:

End Date:

Program Area: Postharvest and Agro-processing

Commodity: Farm machineries, Rice

Objectives:

The main objectives of this research work are

1. to determine the optimum drying temperature of rice seed.

2. to determine the germination percentage of paddy seed dried at three different temperatures.

3. to determine the quality of seed in terms of colour.

Methodology:

Materials: The thin Layer Drying Apparatus installed in Post Harvest Technology laboratory in Farm Power and Machinery Department was used for drying of paddy at 40º C, 50º C, 60º C. Freshly harvested Boro Hybrid SL-8H rice was collected at 9:00 AM from the Agricultural Farm-3 from Bangladesh Agricultural University on April 2010 and at 1:00 PM in the same day it was used for drying. The collected rice seed was cleaned before drying. The initial moisture content of paddy was determined by oven drying method at 130º C for 16 hours (Bala, 1997). Thin Layer Drying Apparatus: Thin layer drying is accomplished under the controlled conditions of drying air temperature, humidity and velocity. To dry rice seed under controlled conditions of air temperature, relative and air velocity, atmospheric air was supplied by a centrifugal fan, 1, through a GI pipe, 2, fitted with an orifice plate, 3 to the bottom of the metal tower, 4 packed with plastic rings, 5. The airflow was measured with U-tube manometer, 6, fitted to the inlet and outlet of the orifice plate. Water was pumped from the water tank, 7 by water pump 8. Water in water tank was heated by a water heater, 9 or cooled by water cooling unit, 10, to the required dew point temperature. The temperature of water in the water tank was controlled by a temperature controller. At the top of the tower, water was sprayed by a nozzle, 11 at the required dew point temperature of the air. The air passing through the packed tower was approximately saturated and was exhausted from the top of the water tower, 12 through GI pipe to the heater box, 13 and was heated to the required temperature by two electric heaters.

Source of Information: A Thesis, Master of Science (M.S.), Department of Farm Power and Machinery, BAU, June-2010

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Thin-layer drying experiments were conducted under three different combinations of temperature with an aim of studying the effects of drying air temperature on the germination percentage of paddy. An increase in drying temperature decreased the drying time and final moisture content of dried paddy. Five thin-layer drying equations were fitted to the experimental data and it is observed that Midilli achieve the highest rank followed by the two-term exponential for different temperatures. Here, the highest R2 (close to 1) and the lowest RMSE values indicate the highest grade point and highest average grade point ranked first. The Midilli was the first in rank and the two-term exponential was ranked second followed by the page, Henderson and Pabis and Newton model. The thin-layer drying equations developed here can be applied to simulate solar drying and optimization of the dryer performance. According to the experimental results, the drying temperature, the initial moisture content of seeds and the drying time had significant effects on the seed quality in terms of germination percentage. It was found that drying temperature of 40ºC germination percentage was highest. Germination percentage decreased with the increase of temperature. Germination curve showed germination percentage changes of seeds as a function of drying temperature and drying time. Colour of paddy did not change with the change of drying temperature. Lightness, hue angle and croma were determined and found almost similar for three different drying temperatures.

Knowledge Management: Thesis