Influence of granule size on physicochemical, structure, microstructure and rheological properties of shiitake mushroom stipe powder

BACKGROUND: The stipe of the shiitake mushroom is rich in nutrients, minerals, amino acids and various volatile and nonvolatile compounds. In this study shiitake mushroom stipe powder (SMSP) was prepared at varying granule sizes (300, 200, 150, 74 μm) via sieving (60, 80, 100 and 200 mesh) and the impact of granule size on physicochemical, rheological, microstructural and thermal properties was comprehensively evaluated. RESULTS: Decreasing granule size significantly (P < 0.05) reduced ash, protein and fat content, while it increased water solubility index, swelling power and color parameters L* (lightness) and b* (yellowness). Water-holding capacity and oil-holding capacity showed no consistent behavior (first increased and then decreased) with decreasing granule size. Rheological analysis revealed SMSP exhibited solid-like behavior, with the 150 μm particle size demonstrating superior viscoelasticity and resistance to deformation. X-ray diffraction indicated reduced crystallinity as particle size decreased. Differential scanning calorimetry showed a thermal transition peak between 84.50 and 92.26 °C for all sizes. All sieved fractions exhibited significantly higher zeta potential values compared to whole powder, indicating enhanced colloidal stability. CONCLUSION: Granule size critically influences the functional properties of SMSP. Finer powders exhibit enhanced solubility, swelling capacity, lightness, yellowness and colloidal stability, alongside altered rheology and reduced crystallinity. The 150 μm fraction demonstrated particularly favorable viscoelastic characteristics. These findings provide essential information for utilizing specific SMSP granule sizes, particularly finer fractions, in developing stable, low-fat and gluten-free food products, leveraging their improved functional attributes. © 2026 Society of Chemical Industry.