Effects of Laboratory Scale Fluidized Bed Heat Treatment on Some Fungal Contamination and Quality of Paddy Seeds

Abstract

The investigation of paddy seed cv. Khao Dawk Mali 105 after harvesting in 2019 season detected various seed-borne fungi, Curvularia sp., Fusarium sp., Aspergillus niger, A. flavus and Penicillium sp. with total infection of 92.25% while germination rate was 93.50%. The effects of heat fluidized bed (FDB) on the reduction of seed-borne fungi on paddy seed were studied using laboratory heat fluidized bed facility (Christison Scientific, UK). The FDB unit was set to a blower speed of 3.7 m/s and then varied combinations of temperature from 60^oC -100 ^oC (5-degree intervals), time periods of 90, 120 seconds and seed loads of 200 g. The results found that, the increasing temperature level was able to significantly reduce the percentage of fungal contamination on the paddy seeds and cause the germination percentage to decrease as well. Using a paddy seed weight of 200 grams, temperature of 65^OC for a period of 120 seconds was the most appropriate trial. This treatment effectively decreased contamination by over 20 % without causing seed germination to be below standard. However, the temperature above 70^oC, the seed germination rate was below 80%, which was not acceptable for the standard germination rate. These results were confirmed in a similar experiment with paddy seed cv. Pathum Thani 1. Additionally, the trial at

a temperature above 85^oC reduced some milling qualities from very good to good on the seed. The effects of FDB on various levels of A. niger contamination including 25%, 50%, 75% and 100% on paddy seed cv. Khao Dawk Mali 105 were established. The results revealed 50% decreasing of fungal contamination on the seed after treatment  with 75-80^oC at all contamination levels.  While, Curvularia sp. and Fusarium sp. were more sensitive to FDB than A. niger, the use of 60^oC exhibited a 50% reduction in contamination in all trials.