# Inactivation of Contaminated Fungi in Rice Grains by Dielectric Heating
## 1 Introduction  
Rice (_Oryza sativa_ L.) is one of the most important grains that feed approximately 75% of the world's population. It is a staple food of Asian countries, including China, India, Indonesia, Bangladesh, Vietnam, Philippines, Thailand, etc. [1, 2]. However, the quality of rice grains can be affected by contaminated fungal contamination _Aspergillus_ species [3, 4]. _Aspergillus_ species contamination levels in brown rice were discovered to be \(10^{3}\) CFU/g [5]. Rice contamination with fungal species during harvest and storage is of poor quality and low economic value. Moreover, it can harm human and animal health [6]. Some fungal species (mainly _Aspergillus flavus_ and _Aspergillus__pansticus_) produce aflatoxin, which are fungal secondary metabolites that contaminate dietary staples worldwide, including maize, rice, and groundnuts [7]. Dietary exposure to aflatoxin is a public health concern due to its acute and chronic carcinogenic effects [8]. Therefore, decontamination of fungi in rice grains before storage or distribution is very important.  
Techniques for fungal decontamination have been reported, including chemical, biological, and physical methods [9]. Various chemicals, such as ozone (O\({}_{3}\)), have the potential to inhibit fungal growth and disrupt mycelial development through oxidation reactions. However, the use of ozone limitations in industrial applications, such as the high-cost requirement for installation and operation [10, 11]. Biological methods, such as temperature, humidity, and other environmental parameters, do not kill or inhibit fungi, especially fungal spores [12]. Interestingly, there are physical mechanisms, such as radio frequencyheating (RFH) and microwave heating (MWH). The methods can potentially damage fungal cells by heat generation [13; 14; 15], which has no toxic residues and no effect on human health. In addition, the rice industry has used RFH and MWH treatments [16; 17; 18].  
RFH and MWH have been used for controlling various fungi in food products. For example, RF treatment used to control _Aspergillus flavus_ in oilseed, wheat, and corn [19; 20] and _Penicillium crustosum_ in chestnuts [21]. The control of _Aspergillus flavus_ and _Aspergillus parasiticus_ in brown rice, barley, and corn [5; 22], _Penicillium_ spp., and _Aspergillus_ spp. in Brazil nut seed shell and kernel has been reported using MW [23]. At the present study, dielectric heating is one of the heating techniques, including RF and MW energy. This technique can convert electrical energies into thermal energy inside the dielectric material. Depending on the electric field frequency, different heat level is generated in the dielectric material [24; 25; 26; 27; 28]. In previous studies, the application of dielectric heating is a selective heating technique for insect control in rice [29; 30; 31; 32; 33; 34; 35; 36; 37]. The method involves heating the insects to a lethal temperature (60 \({}^{\circ}\)C) with exposure time (30 min) and avoiding the heat generated in the rice based on the different dielectric properties [33; 38]. The dielectric loss is the ability to dissipate energy in an applied electric field [31; 33]. The measured dielectric loss is considered to find out the optimal frequency ranges, which leads to efficient heating system.  
This is novel research that aims to optimize the best condition of dielectric heating for fungal control in rice products. The comparative effect of these dielectric heating frequency ranges on fungal growth had not yet been conducted. In addition, the effect of electric field intensity on the heating system is also examined in this study. The information about dielectric properties is an important key for developing dielectric heating industrial equipment in the future.