Synergistic regulation of P. eryngii quality and protein properties by dielectric-guided gradient conversion drying and ultrasound-assisted functional rehydration of by-products.

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Citation abstract

Quality deterioration and underutilization of by-products (Pleurotus eryngii root wastes) limit the industrial drying and protein valorization of Pleurotus eryngii (P. eryngii). This study established a dielectric-guided gradient transition drying (GTD) strategy combined with functional rehydration to address these issues. During the microwave vacuum drying (MVD) process, a transformation node was determined at 60 min based on dielectric properties and low-field nuclear magnetic resonance (LF-NMR). At this node, the tangent value of loss dropped sharply, and the water migration changed from free water to loosely bound water transformation and became dominated by bound water. This transition was used to design GTD schemes that switched from MVD to hot-air microwave drying (HMD). The GTD-1 mode shortened drying time relative to MVD while providing better color and rehydration capacity than HMD and the high-power GTD-2 mode. To enhance protein functionality, processing by-products were rehydrated with sucrose, citric acid, calcium chloride, or tea polyphenols and co-dried with the main product. Structural and functional analyses of the main product protein showed that sucrose and citric acid preserved ordered secondary structures, maintained moderate crystallinity, and improved solubility, water-holding capacity, and emulsifying and foaming properties, whereas calcium ions and tea polyphenols promoted aggregation and crosslinking with mixed effects on functionality. Overall, dielectric-guided GTD-1 combined with functional solutions rehydration offers a practical route to dried P. eryngii with improved product quality and tailored protein functionality.