Food structure plays a key role in the functional properties of food, which are essential for food processing and product development. These structures significantly influence nutrient transport during processing, as food porosity directly impacts the bioavailability of nutrients, including proteins, carbohydrates, lipids, minerals, vitamins, polyphenols, glucosinolates, aroma compounds, and enzymes (Galanakis, 2021). A deeper understanding of food structure, such as the distribution of water and fat within a food matrix, can help optimise processing techniques to preserve the sensory attributes of food, including flavour, aroma, and texture (Aguilera, 2024). The size of pores in plant-based foods varies widely depending on the type of food, its processing, and its structural composition. However, general trends can be classified as micropores (<2 μm), mesopores (2–50 μm), and macropores (>50 μm) (Thommes et al., 2015). The pore size distribution in plant-based foods is essential for understanding the physicochemical transport and storage mechanisms, thus contributing to the optimization of texture, moisture retention, and overall sensory experience, especially in developing plant-based alternatives to traditional animal products Damodaran and Parkin, 2017; Aguilera, 2024; Nwachukwu & Aluko, 2021). Pulses are rich in protein and are ideal for plant-based alternatives to meat products (Prajapati et al., 2024). Pulses are economical sources of essential nutrients globally, and their microstructure significantly influences food quality. This study examines the changes in pore characteristics of peas and pinto beans during RF heating. In pulses, water, fatty acids, proteins, and carbohydrates often coexist to form a complex matrix surrounding pores that are filled with water and air, all of which contribute to the texture, stability, and sensory qualities of the pulses (Shevkani, Singh, Chen, Kaur, & Yu, 2019). Water in pulses is found in both micropores and macropores: in micropores, water molecules are tightly bound within small, compact spaces in the food matrix, while in macropores, water occupies larger cavities where it is more loosely held and can easily move or evaporate (Singh, 2017). Fatty acids coat the pores, influencing moisture retention and playing a key role in the rheological properties of the food sample by affecting its viscosity, stability, and mechanical behaviour (Shevkani et al., 2019). Proteins form a network that defines the elastic structure, and carbohydrates fill the pores, retaining water and providing bulk (Singh, 2017).

X-ray absorption radiography or tomography is a widely used non-destructive method for imaging, especially on dry seeds (Quenot, Bohic and Brun, 2022, Ren et al., 2024, Rousseau et al., 2016; Bino, Aartse, & van der Burg, 1993). The contrast in atomic number, at the physical origin of contrast in X-ray imaging, is strong in dry tissues because of the presence of air networks (Huda & Abrahams, 2015). Also, the contrast in X-ray imaging can be enhanced by using in-line phase contrast tomography with coherent X-ray sources accessible via synchrotron radiation (Quenot, Bohic, & Brun, 2022). The tomographic procedure consists of acquiring projections of an object along with different directions and combining them computationally to obtain a 3D reconstruction of the object (Khan, Yasin, Abid, Shafi, & Khan, 2018). This approach has been successfully used in soft X-ray microscopy, with Fresnel zone plates as objective lenses, providing a unique visualization of a whole cell at 60-nm resolution (Larabell & Le Gros, 2004; Schneider et al., 2010). The coherent diffraction imaging based on phasing a coherent Fraunhofer diffraction pattern (Quenot, Bohic and Brun, 2022, Ren et al., 2024), is expected, in the 3D imaging of tiny isolated biological objects, to overcome the resolution limit set by the X-ray optical devices. Variations in the phase of the beam are sensitive to compositional changes, hence to the object structure. Synchrotron-based studies have provided valuable insights into the internal structure and porosity of seeds. Indore, Karunakaran, and Jayas (2022) reviewed the applications of synchrotron tomography in agriculture and food sciences, emphasizing its role in non-destructive imaging and analysis of seed structures. Dobson et al. (2016) presented a state-of-the-art 4-D imaging methodology using synchrotron X-ray tomography to visualize and quantitatively assess dynamic pore-scale processes in real-time, which aligns with the current study's approach to analyzing pore volumes and voxel counts. Bultreys et al. (2020) verified pore network models of imbibition in rocks using time-resolved synchrotron imaging, highlighting the importance of accurate pore-scale fluid distribution models. These studies corroborate the findings of the current study, underscoring the effectiveness of RF heating and synchrotron imaging in achieving uniform temperature distribution and efficient heat transfer in heterogeneous food matrices. Thus, our approach in developing the methodology for imaging should involve quantitative phase contrast tomography (holotomography) using synchrotron radiation with good spatial coherence. In this approach, spatial variations in the phase of the beam, related to the real part of the material's refractive index, are turned into contrast through Fresnel diffraction (Cloetens et al., 1999). The refractive index of a material for hard X-rays is directly related to its electron density, the result is a 3D representation of the local electron density. This method can analyze whole seeds as they are, without any sample-modifying preparation procedure.

RF heating is dielectric heating and depends on the dielectric properties, specific heat and bulk density of the matter, which generate volumetric heating (Jiao, Tang, Johnson, Tiwari, & Wang, 2011; Shrestha, Yu, & Baik, 2013). During RF heating moisture distribution and interactions with other components such as NFs and ANFs play a crucial role and it is assumed there is no temperature gradient from outside to inside in the sample. During RF heating, micro-explosions of water molecules within the sample are expected, leading to the formation of macropores and macro channels through which water vapour and other volatile compounds escape. These volatiles may include both antinutritional factors (ANFs) and nutritional factors (NFs) present in pulses (Oke, 2021). Understanding the pore characteristics of peas and pinto beans during RF heating is essential for designing an efficient thermal processing system for pulses.

This study investigates pore formation in whole pea and pinto bean seeds subjected to varying moisture contents and RF power levels. It also explores the multiphysics of RF heating, particularly how water molecules within the macropores of these porous seeds are selectively and rapidly heated compared to the surrounding matrix. This phenomenon is further analyzed using computer simulations to better understand the interaction between dielectric heating and pore structure.