Abstract: Lipid oxidation is an important factor causing the quality deterioration of egg yolk powder. In this study, the lipid oxidation process of egg yolk powder was monitored during accelerated storage at 40, 50 or 60 ℃, and a shelf life prediction model was developed and applied to predict the shelf life of egg yolk powder at 25 ℃. The results showed that the acid value (AV), peroxide value (PV), thiobarbituric acid-reactive substances (TBARS) value, p-anisidine value (p-AV) and total oxidation value (TOTOX) of egg yolk powder increased, and the L*, a* and b* values, sensory quality and nutritional value decreased during accelerated storage at all temperatures. The changes of fatty acids in egg yolk powder were analyzed by gas chromatography-mass spectrometry (GC-MS). The relative contents of polyunsaturated fatty acid (PUFA) and monounsaturated fatty acid (MUFA) were found to significantly decrease, while the relative content of saturated fatty acid (SFA) significantly increased after accelerated storage for 35 days compared to fresh egg yolk lipids (P < 0.05). Using Fourier transform infrared (FTIR) spectroscopy, it was found that the structure of lipids in egg yolk powder did not change significantly during accelerated storage, but the intensity of the characteristic absorption peaks changed slightly, which was related to the lipid oxidation of egg yolk powder. Pearson correlation coefficient showed that among all quality indicators, the highest correlation was found between the PV and sensory score of egg yolk powder, so PV can be used as a key indicator of the kinetics of quality deterioration. Kinetic model analysis showed that the change of PV of egg yolk powder was better fitted to a zero-order kinetic model. Based on the Arrhenius equation, the activation energy EA was 19.58 kJ/mol and the pre-exponential factor k2 was 83.93. The predicted shelf life of egg yolk powder was 580 days when stored at 25 ℃, and the relative error between the predicted and actual shelf life was −7.15%. This indicates that the established prediction model could accurately the shelf life of egg yolk powder.

Key words: egg yolk powder; accelerated storage; lipid oxidation; shelf life