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Tropentag, October 5 - 7, 2004 in Berlin

"Rural Poverty Reduction
through Research for Development and Transformation"


Seed Qualities, Chemical Compositions and Dehydrogenase Enzyme Activity of Sesame Seed Affected by Radio Frequency Heat Treatment

Pratchaya Vassanacharoen, Nattasak Krittigamas, Suchada Vearasilp

Chiang Mai University, Department of Agronomy, Thailand


Abstract


Three varieties of sesame seed, Mahasarakam 60 (MK60, white seed), MG 18 (black seed) and Aubon 1 (AU1, red seed) from Thailand with initial seed moisture contents of 5 and 10 percent were treated with radio frequency of 60, 70, 80, 85, 90 degree Celsius for 180 second. The result showed that the initial seed moisture content at 5 percent had decreased to 4.9, 4.6, 4.5, 4.1 percent and at the initial seed moisture content 10 percent had decreased to 9.3, 9.1, 8.8, 8.6, 8.3 percent according to the increasing of the higher level of temperature from 60, 70, 80, 85, 90 degree Celsius. High Radio frequency temperature (85-90 degree Celsius) is the most important factor affecting seed qualities such as seed germination and seed vigour. Whereas the initial seed moisture contents showed no significantly effects. Increasing of radio frequency temperature treatment decreased the percent of germination and seed vigour and leaded to increase the percent of abnormal seedling. The optimum temperature in drying seed by this method was 70 degree Celsius, seed moisture content decreased to 4.6 percent (5 percent initial moisture) and 9.1 percent (10 percent initial moisture), percent of germination were 86 and 85 percent and seed vigour is 69 and 60 percent, respectively. The radio frequency temperature at 85ºC is the critical point, it had significantly affecting on increasing number of abnormal seedling and the chorotic spots were observed on cotyledon. MG18 resulted the best positive response from the radio frequency drying treatment (70 degree Celsius) with 88 percent of germination and 75 percent of seed vigorous. Beside that, the treatments did not show any significant changes in seed chemical compositions such as free fatty acid, total carbohydrate and protein content, but at the level of 70 degree Celsius treatment, it had significantly enhanced on dehydrogenase enzyme activities. Anyhow, the application at the temperature above 85 degree Celsius had reverse effects.


Keywords: Carbohydrate, dehydrogenase, free fatty acid, germination, protein, radio frequency, seed quality, seed vigour, sesame seed


Contact Address: Pratchaya Vassanacharoen, Chiang Mai University, Department of Agronomy, Chiang Mai, Thailand, e-mail: pratchaya17@yahoo.com


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