Effects of NaCl on the Freezing-Thawing Induced Gelation of Egg Yolk at pH 2.0–8.0

During the freezing preservation of egg yolk, the functionalities of egg yolk become weakened due to freezing-thawing induced yolk gelation (FTYG). FTYG can be inhibited by adding NaCl. However, the physicochemical mechanism of NaCl is not fully understood yet. The effects of NaCl on FTYG were investigated in this study at different pHs. Decreasing pH to 2.0 to 3.0 caused the release of Ca2+ and the dissociation of yolk granules, and the addition of NaCl at this pH range resulted in the re-aggregation of dissociated granules and the promotion of FTYG due to the charge screening effect. On the other hand, at pH 4.0–8.0, the addition of NaCl led to the dissociation of granules due to the displacement of Ca2+ by Na+ in the calcium bridges, consequently leading to the inhibition of FTYG. The differed effect of NaCl indicated the NaCl modulated the FTYG by strengthening or weakening the filler effect of granules in yolk gel. Our findings suggested that weakening the filler effect of granules is a promising method to inhibit FTYG.