Buckwheat (Fagopyrum spp.), as a pseudocereal, can grow worldwide due to their strong adaptability to various environments (Ge & Wang, 2020). Common buckwheat has been proved to be one of species containing rich nutrition and high functional components for human health. Therefore, the interest on using common buckwheat increases sharply (Huda et al., 2021). As starch is the principal element of buckwheat kernels, accounting about 70% dry basis, buckwheat can be used as the basic ingredient of a range of staple foods, such as breads, noodles, and cakes (Gao et al., 2020). Buckwheat kernel or flour has low moisture content, which is not conducive to microbial growth. However, when they are mixed with water during processing, the initial microbial counts may increase rapidly and lead to safety problems along the process and even in transport and consumption (Ozturk, Kong, Singh, Kuzy, & Li, 2017). Therefore, buckwheat kernels need to be decontaminated before grinding or consumption (Xu et al., 2022).

Thermal and nonthermal processing methods including superheated steam, microwave, radio frequency (RF), cold plasma, gamma irradiation, and ultraviolet (UV) radiation are the common techniques used for the inactivation of microorganisms (Aaliya et al., 2021; Sánchez-Maldonado, Lee, & Farber, 2018). Among them, RF heating and UV radiation are the new, effective, and promising technologies for the decontamination of grains. Xu, Xu, Guan, Yang, and Wang (2023) have found that the combination treatment of RF and UV can obviously improve the efficiency of microbial inactivation. But in the decontamination process, possible changes in functional properties and molecular structures of the raw material may affect industrial applications eventually (Huang, Guo, Manzoor, Chen, & Xu, 2021; Subedi, Du, Prasad, Yadav, & Roopesh, 2020). Therefore, besides improving food safety, the quality of the final products should also be considered from multiple perspectives, including the properties of starch and protein.

RF technology is the non-ionizing electromagnetic wave with a frequency ranging from 3 kHz to 300 MHz, which can provide rapid and volumetric heating for the whole material (Huang, Marra, Subbiah, & Wang, 2018). As a thermal treatment technique, RF heating usually denatures the protein and causes rearrangement of the intramolecular structures of starch, which can be detected by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Besides, Zhou, Yang, Tian, Kang, and Wang (2023) have also found additional effects on the multi-scale structures of starch due to molecular vibrations during RF processing. Therefore, in addition to the regular applications of pasteurization (Jiao, Zhang, Liao, Hayouka, & Jing, 2021), drying (Elik, 2021), and blanching (Manzocco, Anese, & Nicoli, 2008), RF treatments can also be used for regulating the functions and properties of protein and starch (Ling, Ouyang, & Wang, 2019; Ma et al., 2022), such as hydration, viscosity, and rheological properties. But most of reported studies are based on single ingredient, and the effects on the whole grains are still limited.

UV radiation is a part of the electromagnetic spectrum with the wave range from 100 to 400 nm and most commonly with UV-C (200–280 nm), which is widely known for the photochemical reactions. Previous reports have shown that OH, SS, and CH bonds can be formed or degraded when exposing to UV light (Kumar, Nayak, Purohit, & Rao, 2021). Thus, extensive studies have been conducted to exploit the potential employments of UV radiation for microbial inactivation, and modification in starch and protein structures. Neves-Petersen, Gajula, and Petersen (2012) have reported that 22 potential amino acids possess the ability to absorb UV radiation and undergo photochemical reactions to change structures of protein. Moreover, UV induced photo-degradation of starch extracted from wheat, maize, potato, and other biological sources has been demonstrated earlier (Kurdziel, Labanowska, Pietrzyk, Sobolewska-Zielińska, & Michalec, 2019). In the case of cereals, current researches are mainly focused on the microbiological safety after UV exposure. The effects of UV radiation on physicochemical properties of grain, especially for the buckwheat, have not been reported.

In addition, a combination of thermal and nonthermal technologies has also been applied to modify starches or proteins from different sources (Lima et al., 2021). Nevertheless, studies about effects of combined RF and UV treatments on these quality characteristics are limited. Considering that the combination treatment can improve the efficiency of decontamination, it is important to explore the changes of quality characteristics of buckwheat after RF and UV treatments for verifying its suitability of industrial applications.

Consequently, the aims of the present study were to (1) analyze effects of RF and UV treatments developed for effective food decontamination on the hydration, viscosity, rheological properties, morphological, crystalline, and molecular structures of buckwheat, and (2) compare with the single RF or UV treatment, and systematically explore whether there were additional effects of the combination treatment on structures and physicochemical properties of buckwheat.