Determining Radio Frequency Heating Uniformity of Mixed Beans for Disinfestation Treatments

Abstract

Chickpeas and lentils are two important legumes grown in the U.S. that need phytosanitary treatments before export to several countries, 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 pea (moisture content of 8.8% w.b.) were 65 C higher than those in chickpea (moisture content of 7.0% w.b.), while after 10 min of RF heating mung bean temperatures (moisture content of 10.2% w.b.) were 45 C higher than lentil temperatures (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% w.b., respectively, their final temperatures were about 3.55 C and 3.75 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 in chickpea and lentil.

Simulation and prediction of radio frequency heating in dry soybeans

“…To meet phytosanitary and quarantine regulations for international trade, there is an urgent need in developing nonchemical postharvest pest control methods for dry soybeans. Radio frequency (RF) energy is an electromagnetic wave with a frequency of 1e300 MHz, which provides rapid and volumetric heating, and has been studied as a non-chemical alternative for postharvest insect control in dry products (Halverson, Burkholder, Bigelow, Nordheim, & Misenheimer, 1996;Nelson, 1973;Tang, Ikediala, Wang, Hansen, & Cavalieri, 2000), such as alfalfa seed (Yang, Zhao, & Wells, 2003), grain (Nelson, 1996), legume (Jiao, Tang, Johnson, Tiwari, & Wang, 2011;Wang, Tiwari, Jiao, Johnson, & Tang, 2010), lentil (Jiao, Johnson, Tang, & Wang, 2012), rice (Lagunas-Solar et al, 2007;Zhao, Qiu, Xiong, & Cheng, 2007), walnut (Mitcham et al, 2004;Wang et al, 2001;Wang, Monzon, Johnson, Mitcham, & Tang, 2007a, b;Wang et al, 2006), and wheat (Halverson et al, 1996). The relatively long wavelength of RF usually results in deep penetration depth and predictable temperature profiles in foods, but the nonuniform heating is still a problem for RF heating technology to be applicable in the food industry (Tang et al, 2000;Wang et al, 2007a).…”

Dielectric properties of corn flour from 0.2 to 10GHz

“…These measurements were made in a wide range of moisture content, temperature and at density equivalent to density of respective cereal grain; so as the determined data can be applied to corresponding grains/cereals for various applications particularly for postharvest pest control (Nelson and Whitney, 1960;Nelson, 1976;Wang et al, 2003a;Jiao et al, 2011;Shrestha and Baik, 2013). There is also a dire need to develop such applicators for cereal grain flours.…”

Coffee Bean Heating Uniformity and Quality as Influenced by Radio Frequency Treatments for Postharvest Disinfestations

“…Recently, RF treatments have been developed to control codling moth (Wang et al, 2001) and navel orangeworm (Wang et al, 2002(Wang et al, , 2007a(Wang et al, , 2007bMitcham et al, 2004;Gao et al, 2010) in in-shell walnuts and almonds. Available research results on RF heating for low-moisture products Jiao et al, 2011aJiao et al, , 2011b) have shown its potential as an environmentally friendly pest-control method in coffee beans.…”