Study on effect of salting process on egg yolk plasma using AF4 combined with ATR-FTIR and DSC

In this work, the effect of salting method (i.e. immersing method and paste coating method) and salting time on egg yolk plasma was studied. Asymmetrical flow field-flow fractionation (AF4) combined with attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR) was employed for monitoring low density lipoprotein (LDL) aggregation in salted egg yolk plasma. AF4 provides a size-based separation of the major components of egg yolk plasma. ATR-FTIR allows determining the secondary structure of protein such as intermolecular beta-sheet structure which is an indicator of protein aggregation. By combining the results from AF4 and ATR-FTIR, it was clearly demonstrated that salting process results in the formation of LDL aggregates. Furthermore, the LDL size distributions of a variety of egg yolk plasmas were obtained based on AF4 theory. Results reveal that the size distribution of LDL in duck egg yolk plasma is broader than that in hen egg yolk plasma. The protein thermal stability of salted egg yolk plasma was investigated using differential scanning calorimetry (DSC). It was found that salting process enhances the thermal stability of egg yolk plasma. The results show that AF4 combined with ATR-FTIR and DSC is a promising approach towards better understanding of protein aggregation.