Nutrient migration and lipidomics changes in the liquid inner core of alkali-pickled duck egg yolk

Preserved duck egg yolk (PEY) can be divided into a solidified outer layer (S-PEY) and a liquid inner core (L-PEY) during the middle-later stages of alkaline pickling. The differences among PEY, S-PEY, and L-PEY were systematically investigated using property characterization, nutrient determination, and lipidomics analysis. The results demonstrated that L-PEY exhibited a more vivid red-yellow color, with higher total protein, total lipid, and phosphorus contents compared to S-PEY. Conversely, the pH, moisture, and sodium contents were higher in S-PEY than in L-PEY. Quantitative lipidomics analysis revealed that L-PEY possessed a significantly higher total lipid abundance than PEY, with 19 lipid subclasses (551 lipid molecules) being notably more abundant in L-PEY. Phospholipids exhibited the most significant differential abundance, with the abundance of phosphatidylethanolamines (PE) and phosphatidylcholines (PC) in L-PEY being 19.6 and 13.6 times greater than those in S-PEY, respectively. These findings indicated that the alkaline pickling procedure resulted in substantial nutrient migration duck egg yolk, particularly in the case of phospholipids. The results provide novel insights into the processing mechanism of preserved duck egg yolk.