Changes of physicochemical properties of salted egg yolk during rapid curing development

In this study, fresh egg yolk was used as raw material, and the yolk was put into a customized mold according to the amount of salt and the mass ratio of egg yolk (1%, 3%, 5%, 7% and 9%), and the curing time was 1, 3, 5 and 7 days, respectively. In order to investigate the effects of salt content and salting time on the morphology and physicochemical properties of salted egg yolk in the unilateral curing process with salt added on the top surface of salted egg yolk. At the same time, in order to prove the feasibility of the experiment and select the optimal conditions for samples and commercial samples yield efficiency, the sand, sensory evaluation was carried out for quality analysis. In the process of salted egg yolk, salt constantly penetrates into the yolk, resulting in constant water loss of the yolk, shrinkage and change of the yolk, protein aggregation, and deepening of the color of the yolk. The results of low field NMR showed that during the salting process, the infiltration of salt led to the increase of free water fluidity, and the water in the yolk constantly migrated to the outside of the yolk membrane. The imaging results are more intuitive and clear. It can be seen that the moisture content of egg yolk decreases significantly. The increased amount of salt added and prolongation of salting time will accelerate the water migration rate. Atomic absorption results showed that the Na+ content in the center of egg yolk increased significantly with the prolongation of curing time. The more salt was added was, the longer the curing time was, the faster the salt migration speed was. Color difference results showed that during the curing process of salty egg yolk, the natural pigment in egg yolk is further enriched due to the dehydration of egg yolk, which leads to the deepening of egg yolk color. The results of texture showed that the egg yolk protein was aggregated due to the outward migration of water and inward infiltration of salt, and the hardness of egg yolk was strengthened and its elasticity was weakened. After screening, when the curing time is 7 days, the amount of salt added is 3%, or the curing time is 3 days, the amount of salt added is 5%, the whole salted and separated egg yolk product on the market is more similar. In order to verify the credibility of the results, the oil yield, sand removal and sensory evaluation quality of the most similar test samples and the commercial products were analyzed and compared again. The results showed that there was no significant difference between the test samples and the commercial samples (P<0.05), which further provided theoretical feasibility for the single-side salted egg yolk technology. The existing egg processing equipment provides good equipment support for the industrial production of salted egg yolk, which can quickly and batch prepare salted egg yolk products, so as to provide data support and theoretical basis for the industrial production of salted egg yolk in the future.