Autoclave-assisted green extraction of a hierarchical self-assembling polysaccharide from Flammulina velutipes Mycelium for ultra-efficient cryoprotection of frozen egg yolk

This study developed a novel autoclave-assisted extraction technology to isolate a cryo-active polysaccharide (FVP-N1) from Flammulina velutipes mycelium and evaluated its potential as a natural cryoprotectant. FVP-N1 demonstrated significant ice recrystallization inhibition (IRI) activity, reducing ice crystal size by 92.38% compared to the control. Structural analysis identified FVP-N1 as a heteropolysaccharide (MW: 6.76×10 5 Da) composed of glucose, xylose, and mannose (molar ratio 44.11:36.82:14.93), featuring a backbone of 1,3,4-linked α-D-glucopyranosyl residues interspersed with 1,3-linked α-D-mannopyranosyl units. Critical structural motifs included O4-branched side chains terminated by β-D-xylopyranosyl residues. Morphological studies (SEM/AFM) revealed hierarchical self-assembly into porous lamellar sheets aggregated into spherical clusters interconnected by fibrillar chains, suggesting a dual IRI mechanism involving ice surface adsorption and hydrogen-bond-mediated water ordering. Notably, FVP-N1 at an ultra-low concentration (0.005% w/v) effectively maintained fluidity, protein solubility, and moisture homogeneity in frozen egg yolk. These findings elucidate the ​​structure-function relationship of FVP-N1 and validate its practical utility as a highly effective, natural cryoprotectant for industrial frozen food applications.