Unveiling the texture formation mechanism in Chinese yam — How the sublimation–evaporation transition temperature governs multiphase microwave drying

This study investigates how the sublimation–evaporation transition temperature (T S-E ) regulates multiscale texture formation in Chinese yam during multiphase microwave drying (MMD). Two representative T S-E conditions were selected: −6 ℃ (T−6), representing a state with substantial ice crystal retention, and −3 ℃ (T−3), a critical point where significant ice melting occurs. Structural and mechanical changes were assessed across multiple scales using X-ray micro-computed tomography (μCT), texture profile analysis, stress relaxation tests, cellular morphology observation, and water-soluble pectin (WSP) galacturonic acid (GalA) quantification. The T−3 condition effectively preserved cellular integrity, resulting in higher retention of WSP. This molecular preservation supported the formation of a rigid, honeycomb-like porous skeleton with superior viscoelastic properties. Specifically, the T−3 group yielded significantly higher residual and relaxation moduli ( E 0 , E 1 , P < 0.05) and an enhanced interconnected pore volume (526.27 ± 20.61 mm 3 ) compared to the T−6 group (410.29 ± 47.30 mm 3 ). Consequently, these samples exhibited high brittleness with lower hardness and more fracture peaks. Conversely, the T−6 condition caused early ice melting and severe water plasticization, leading to macroscopic structural collapse. Furthermore, both conditions exhibited late-stage pore refilling and structural stabilization, with T−6 showing a significantly higher filling density than T−3. These findings provide a robust theoretical basis for precise texture customization in dried foods by manipulating multiscale structural stability via T S-E .