Development of an innovative process for salted egg yolk powder with improved physicochemical properties using protease hydrolysis

Salted egg yolk powder (SEYP), one of the derivatives of salted egg yolk, has a long preparation cycle and low solubility, which affects its application in the food industry. Here, we suggest to directly marinated the egg yolk liquid to shorten the production process of SEYPs, and then hydrolyze the salted egg yolk liquid using pH in synergy with acidic, neutral and alkaline protease to obtain SEYPs with better physicochemical properties. The results showed that the best performance and color of SEYPs were obtained under the conditions of 4% salt concentration, 2% baijiu (Chinese liquor) addition, 0.2 mL/50 g spice addition, and 2 d marinating time. Meanwhile, the addition of protease significantly reduced the aggregation of flocs and significantly increased the solubility compared with unhydrolyzed SEYPs, which was confirmed by the solubility and surface hydrophobicity. SDS-PAGE showed that the proteins were decomposed into smaller peptides, and the content of soluble proteins increased as a result. The FTIR results showed an increasing trend of β-folding in all treatment groups, indicating that the protease disrupted the original conformation of the proteins and facilitated the process of formation of a more disordered structure of the yolk proteins, with a sparser structure of the SEYPs. Moreover, there was little difference in the color of SEYPs. In conclusion, the direct preparation of SEYPs by enzymatic treatment of egg yolk liquid provides a theoretical basis for improving the quality of SEYPs.