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ARS Home » Pacific West Area » Parlier, California » San Joaquin Valley Agricultural Sciences Center » Commodity Protection and Quality Research » Research » Publications at this Location » Publication #258620
Title: Determining radio frequency heating uniformity of mixed beans for disinfestation treatments

Author
item JIAO, S - Washington State University
item TANG, J - Washington State University
item Johnson, Judy
item TIWARI, G - Washington State University
item WANG, S - Washington State University

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2011
Publication Date: 10/25/2011
Citation: Jiao, S., Tang, J., Johnson, J.A., Tiwari, G., Wang, S. 2011. Determining radio frequency heating uniformity of mixed beans for disinfestation treatments. Transactions of the ASABE. 54(5):1847-1855.

Interpretive Summary: The occurrence of natural field infestations of cowpea weevil in chickpea and lentil, requires the US legume industry to meet postharvest phytosanitary regulations before export to foreign markets. The most common method for postharvest insect control in legumes relied on chemical fumigants, but various environmental and regulatory concerns has generated interest in non-chemical alternatives. Radio frequency (RF) heating has potential as an alternative method for insect control in legumes. Because black-eyed peas and mung beans are more readily infested by cowpea weevil, these were selected as possible surrogate legumes during RF disinfestation studies. To evaluate the suitability of black-eyed peas and mung beans as surrogates, their thermal and dielectric properties at selected moisture contents were measured and compared with those of chickpeas and lentils. Temperature differences between black-eyed pea and chickpea or between mung bean and lentil were determined in a pilot-scale 27 MHz RF unit. The results showed that the dielectric constant and loss factor of black-eyed pea and mung bean increased with increasing moisture content and temperature, which was in good agreement with the trends observed in chickpea and lentil. After 6 min of RF heating, temperatures in black-eyed peas (moisture content of 8.8% w.b.) were 6°C higher than those in chickpea (moisture content of 7.0% w.b.), while after 10 min of RF heating mung bean (moisture content of 10.2% w.b.) temperatures were 4°C higher than lentils (moisture content of 7.1% w.b.) under the same treatment conditions. By reducing the moisture contents in black-eyed pea and mung bean to 2.6% and 3.7%, respectively, their final temperatures were about 3.5 and 3.7°C lower than those of chickpea and lentil. This would result in conservative insect mortality results when using black-eyed pea and mung bean as surrogate hosts for validation of pest control treatments for chickpea and lentil.

Technical Abstract: Chickpeas and lentils are two important legumes grown in the US and need phytosanitary treatments before exportation, but it is difficult to artificially infest them with live cowpea weevil for radio frequency (RF) treatment validation. To evaluate the more readily infested black-eyed peas and mung beans as surrogates for chickpeas and lentils, the thermal and dielectric properties of black-eyed peas and mung beans at selected moisture contents were measured and compared with those of chickpeas and lentils. Temperature differences between black-eyed pea and chickpea or between mung bean and lentil were determined in a pilot-scale 27 MHz RF unit. The results showed that the dielectric constant and loss factor of black-eyed pea and mung bean increased with increasing moisture content and temperature, which was in good agreement with the trends observed in chickpea and lentil. After 6 min of RF heating, temperatures in black-eyed peas (moisture content of 8.8% w.b.) were 6°C higher than those in chickpea (moisture content of 7.0% w.b.), while after 10 min of RF heating mung bean (moisture content of 10.2% w.b.) temperatures were 4°C higher than lentils (moisture content of 7.1% w.b.) under the same treatment conditions. By reducing the moisture contents in black-eyed pea and mung bean to 2.6% and 3.7%, respectively, their final temperatures were about 3.5 and 3.7°C lower than those of chickpea and lentil. This would result in conservative insect mortality results when using black-eyed pea and mung bean as surrogate hosts for validation of pest control treatments for chickpea and lentil.