Egg White Matters: Studying the Role of Genetic Line and Egg Chilling Storage on the Rheology of Thick Egg White Supporting Meringue Texture

The thick white fraction of albumen (or egg white) is critical for maintaining the high quality and freshness of eggs during storage, but there is limited understanding of how storage affects the rheological behavior of this important gel. This study aimed to investigate the impact of egg storage time on the viscoelastic properties of the thick egg white (TKEW) fraction from two genetic lines (ISA-White (W) and ISA-Brown (B) hens), assessing the modification mechanisms through the analysis of microstructural characteristics. Haugh units (HU) and foaming properties of albumen were also determined. Experiments were conducted after laying (Day 0) and after 15 and 30 days of egg chilling storage. The effects of storage duration on the TKEW viscoelastic properties differed between the W and B lines, causing an increase and a decrease in gel strength (a slope) of the W and B thick albumen, respectively. These findings, together with the microstructure analysis, indicated that after 30 days of storage, the W TKEW developed a more elastic (lower loss factor, tan δ) but brittle (lower strain amplitude, γ_max) albumen network structure, whereas the B TKEW exhibited a weaker but much more deformable (higher γ_max) structure. The textural properties of freshly made meringue batters containing chilled whole egg white (EW) presented similar behavior, supported by the microstructural features observed in foams and batters. Additionally, the W TKEW showed higher HU, and the W EW produced a more stable foam (FS) during storage, although its foam capacity (FC) was lower than that of the whole albumen from the B genetic line.