Five-stage gelation dynamics in thermally driven egg yolk-granule suspensions

The thermal gelation of yolk-granules, a protein-fat hybrid assembly found in egg yolk, is investigated employing X-ray photon correlation spectroscopy (XPCS). Time-resolved dynamics reveal five regimes during heat-induced gelation: regime-A, temperature-driven fast granule motion; regime-B, protein denaturation and aggregation; regime-C, protein gelation; and post-gelation regime-D and regime-E, marked by decreasing and increasing relaxation times, respectively. Compared with whole egg yolk, yolk-granules exhibit distinct microscopic dynamics and aging. At room temperature, yolk-granules show purely diffusive motion, whereas whole egg yolk displays hyper-diffusive behavior. During aging, whole egg yolk follows power-law relaxation, while yolk-granules exhibit non-monotonic relaxation through regimes D and E. The sol-gel transition time follows Arrhenius behavior with an apparent activation energy of 660 ± 10 kJ mol^-1, substantially higher than whole egg yolk (450 ± 20 kJ mol^-1). The D-to-E crossover also follows Arrhenius behavior, with an apparent activation energy of 325 ± 40 kJ mol^-1, illustrating an activation energy-driven process after the gel formation.