Microwaves, operating at frequencies between 300 MHz to 300 GHz, are a form of electronic waves. According to the specific regulations by the U.S. Federal Communications Commission (FCC), domestic microwave ovens typically operate at 2.45 GHz, while industrial applications often employ a frequency of 915 MHz (Tang, 2015). Owing to their longer wavelengths compared to other types of electromagnetic radiation, such as infrared or far-infrared, microwaves possess superior penetration capabilities (Datta & Davidson, 2000). Microwave heating is widely employed in the food industry for various purposes such as thawing/defrosting, tempering, drying, freeze-drying, blanching, cooking, baking, and heating (Chandrasekaran, Ramanathan, & Basak, 2013; Guo, Sun, Cheng, & Han, 2017; Hamoud-Agha, Curet, Simonin, & Boillereaux, 2013). It offers advantages regarding time and energy, as well as improved final product quality (regarding taste, color, and nutritional value) owing to rapid heat generation. Unlike conventional heating, microwave heating enhances energy efficiency by reducing processing time (Kutlu et al., 2022). However, the non-uniform heat distribution of microwave heating is the primary challenge causing hot and cold spots in the product (Portela, Monteiro, & Abreu, 2019). This limitation hinders the effectiveness of microwave pasteurization/sterilization, particularly for cooking foods containing raw ingredients, as it may allow the survival of pathogenic bacteria in less heated zones (Datta & Anantheswaran, 2001; Guo et al., 2017; Sheen et al., 2012; Vadivambal & Jayas, 2010).

A novel thermal processing technology, known as microwave-assisted induction heating (MAIH), has been developed by Chang, Chin, Yu, Hsieh, and Lin (2018), featuring a microwave heating unit on the top and an electromagnetic induction heating element on the bottom (Fig. 1a). In the induction heating part, the sealed crystallized polyethylene terephthalate (CPET) container containing sample was placed in the induction half-cavity, so that the CPET container is close to its inner wall. The body of induction half-cavity is made of metal material with good thermal conductivity, which is acceptable for the induction heating; therefore, the induction heating unit can heat the sample of the CPET container in the form of conduction (Fig. 1b). When the food sample is heated to a temperature close to or even above 100 °C, the generated hot vapor expands the volume causing the CPET container to generate an external pressure. The locked induction half-cavity upper cover and induction half-cavity have sufficient mechanical strength to resist the structural deformation of the CPET container and avoid leakage (Fig. 1b). Since the MAIH system operates at lower atmospheric pressure and does not require additional high-pressure steam or water chambers, it offers several advantages, such as the ability to exceed temperatures of 100 °C, high heating efficiency, rapid temperature rise, operation at atmospheric pressure, and uniform heat distribution (Lee, Tsai, Hwang, Lin, & Huang, 2022; Tsai et al., 2021). Previous studies have confirmed that this MAIH technology achieved uniform heating, rapid temperature increases, and simultaneous cooking and pasteurization of white shrimp, significantly reducing the time required to reach target temperatures (Tsai et al., 2021). Compared to conventional cooking, the volumetric heat produced by the MAIH system improves the heat transfer rate and cuts the total heating time in half. MAIH-treated white shrimp demonstrate delayed microbial growth and a slower decline in freshness during refrigeration, thus extending storage life (Lee et al., 2022). Additionally, when clams underwent MAIH at 130 °C for 110 s or 90 °C for 130 s, it effectively facilitated shell opening and pasteurization (Lee et al., 2021). This technology also mitigated the deterioration in microbial, physical, and chemical quality during storage (Tsai et al., 2022). Moreover, MAIH preserved the physical and chemical quality of barramundi meat during refrigeration, maintaining a superior appearance, color, and texture (Hwang et al., 2023). Hence, MAIH technology has been proven to be an innovative thermal processing approach applicable to seafood.

Rice, like wheat and corn, is one of the highest-yielding grain crops in the world. It has a global production of millions of tons annually and serves as the main staple food for over half of the world's population (Muthayya, Sugimoto, Montgomery, & Maberly, 2014). Rice is grown in >100 countries, among which Asian countries account for the majority of production (Albaridi, Noah Badr, Salama Ali, & Gamal Shehata, 2022). In Taiwan, rice is an extremely important crop and one in which the country has achieved self-sufficiency (Gavahian, Brijesh Kumar, Chu, Ting, & Farahnaky, 2019). Similar to wheat, rice is a healthy grain rich in carbohydrates and proteins, and thus can satisfy various nutritional needs. Ready-to-eat (RTE) meals are precooked and prepackaged food products that can be directly consumed after reheating without additional preparation or cooking (Huang & Hwang, 2012). They represent the next major trend in the food industry and a new option for the satisfaction of current consumer demands. Over the past few years, the proportion of consumers that eat convenience foods has grown by nearly 50% (Sloan, 2019). Further efforts are required to improve the quality, convenience, and storage stability of RTE meals to promote further growth of this sector in the food industry. However, traditional food processing techniques such as cooking, retorting, and freezing pose limitations to the production of high-quality RTE meals with an extended shelf-life (Stanley & Petersen, 2017).

Limited research exploring the impact of microwave processing on the microbial, physical, and chemical properties of rice exists (Auksornsri & Songsermpong, 2017), with no prior studies focusing specifically on microwave-processed ready-to-eat rice. A recent study has indicated that white rice, treated with MAIH, can be fully cooked and free of microbial presence (Lee, Hwang, & Huang, 2024). This study aims to examine whether ready-to-eat rice prepared with MAIH outperforms traditional steaming in terms of delaying quality degradation during storage, thereby extending shelf life. The rice cooked under optimal MAIH conditions (120 °C for 240 s and 100 °C for 300 s) as identified by Lee et al. (2024), alongside rice prepared using conventional steaming methods (100 °C for 30 min), was stored at 35 °C, 25 °C, and 4 °C. The study periodically assessed changes in microbial counts, as well as physical and chemical quality parameters.