Effects of temperature, moisture, and metal salt content on dielectric properties of rice bran associated with radio frequency heating

Abstract

Dielectric heating including microwave (MW) and radio frequency (RF) energy has been regarded as alternative thermal treatments for food processing. To develop effective rice bran (RB) stabilization treatments based on RF and MW heating, dielectric properties (DPs) with dielectric constant (ε′) and loss factor (ε″) of RB samples at frequencies (10–3000 MHz), temperatures (25–100 °C), moisture content (MC, 10.36–24.69% w.b.) and three metal salt levels (0.05–2.00%) were determined by an open-ended coaxial probe and impedance analyzer. Results indicated that both ε′ and ε″ of RB samples increased with increasing temperature and MC. The increase rate was greater at higher temperature and moisture levels than at lower levels, especially at frequencies lower than 300 MHz. Cubic order models were developed to best fit the relationship between DPs of RB samples and temperature/MC at five frequencies with R2 greater than 0.994. Both ε″ and RF heating rate of RB samples increased significantly with added NaCl (2%), KCl (1%) and Na6O18P6 (2%). The obtained data are useful in developing computer models and simulating dielectric heating for RB stabilization and may also provide theoretical basis for synergistic stabilization of RB under combined dielectric heating with metal salts.

Hot air–assisted radio frequency hybrid technology for inactivating lipase in pearl millet

“…On the other hand, enhancement in the HARF exposure period (more than 15 min) showed undesirable changes in nutritional attributes of pearl millet. In recent studies, similar trends were also established for RF-treated rice bran (Liao et al, 2020;Ling, Liu, et al, 2018;Ling Lyng et al, 2018a); and wheat germ (Ling et al, 2018b(Ling et al, , 2020.…”

Effect of extrusion on physical and chemical properties and storage stability of corn germ

“…Extrusion treatment was observed to be an effective method for corn germ stabilization, and extrusion temperature plays a more important role. As is shown in Table . 3 and Figure 5, the effect of extrusion temperature on FFA content is almost consistent with the change of LA activity, and the LA and LOX in corn germ could catalyze the degradation and oxidation of fat components and produce FFA, resulting in the accumulation of aldehydes, which further affects the smell and quality of corn germ (Ling et al, 2018). The shelf lives of extruded corn germ were predicted according to different storage temperatures in 50% relative humidity.…”

Rice Bran Stabilisation and Oil Extraction Using the Microwave-Assisted Method and Its Effects on GABA and Gamma-Oryzanol Compounds

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