Hydration and Structural Changes of Almonds During Water Treatment at Different Temperatures Investigated by MRI and NMR

Hydration and water uptake during blanching critically influence texture and stability of almonds, yet the multiscale structural changes remain poorly characterized. This study employs in situ magnetic resonance imaging (MRI) and ex situ nuclear magnetic resonance (NMR) techniques to provide a comprehensive analysis from millimeter to micrometer scales. The objective was to quantify how water penetrates and reorganizes almond tissue and how these changes affect the microstructural organization of lipids and intrinsic molecular mobility. In situ MRI at 200 MHz was used to monitor water front propagation, swelling, cavity formation, and local relaxation changes in almonds at 20–80°C. Radial signal profiles were analyzed with Boltzmann fits to extract characteristic kinetic parameters, revealing temperature‐dependent hydration dynamics and hierarchical swelling behavior. Ex situ NMR, including pulsed field gradient stimulated echo (PFG‐STE) diffusion and Carr–Purcell–Meiboom–Gill (CPMG) transverse relaxation experiments at 400 MHz, probed lipid mobility and microstructural organization in untreated, industrially blanched, and self‐blanched almonds (4 min and 3 h at 80°C). Results indicate that short‐term blanching preserves diffusion behavior consistent with geometrically restricted lipids in intact oleosomes. In contrast, prolonged blanching (3 h) produces diffusion‐time‐dependent apparent diameters and rapidly relaxing components, suggesting increased water–matrix interactions and structural heterogeneity. Overall, the combined MRI and NMR approach enables linking macroscopic hydration dynamics to microscopic molecular mobility, providing a multiscale understanding of almond swelling and lipid redistribution. These methods offer a robust framework for studying hierarchical structural changes in plant‐based foods under thermal treatment. Practical Applications : The insights into almond hydration, swelling, and lipid mobility obtained via in situ MRI and ex situ NMR are directly relevant for industrial processes, such as blanching and pasteurization. Understanding how water penetrates and interacts with the almond matrix enables optimization of processing parameters to maintain texture, prevent defects, and preserve lipid integrity. These measurements also provide a nondestructive way to monitor batch‐to‐batch variability and can inform the design of novel nut‐based products, improve shelf‐life stability, and be extended to other nuts and seeds where water–matrix interactions influence processing outcomes.