Improving the quality of egg yolk granules via cryogenic processing: A comprehensive analysis of structural, physicochemical, and functional properties.

Egg yolk granules (EYGs) show great potential in the functional food and pharmaceutical industries, but their limited functionality restricts broader applications. This study investigates the effects of various freezing pretreatments on lyophilized EYGs, comparing prefreezing at -20 °C and - 80 °C, immersion in liquid nitrogen (LN), and grinding in LN. SEM, FTIR, and LF-NMR analyses showed that conventional freezing generated large ice crystals, compromising EYGs' properties. In contrast, LN immersion produced tiny crystals that preserved structural integrity and increased surface area, enhancing drying and molecular interactions. LN-immersed EYGs exhibited improved protein solubility (∼80 %), structural flexibility (∼11 %), surface hydrophobicity, emulsification properties (>20 %), and water distribution compared to freezing at -20 °C. Additional enhancements were observed, including α-helix content (∼19 %), ζ-potential (∼19 %), water/oil-binding capacities (∼11 %), sulfhydryl groups (∼3 %), and tyrosine content (∼20 %). This research demonstrates that rapid freezing effectively preserves EYGs' functional and structural characteristics, expanding their potential for broader industrial applications.