| Salted egg yolk has been well received by consumers for the unique sand texture and flavor. A traditional production is to make whole duck eggs preserved, then discard egg white until maturity to get salted egg yolk. However, it takes a long time and it is difficult for salted egg white to be used in food processing, which leads to a resource waste and poses a threat to an ecological environment. Concerning an increasingly tight market of the salted egg yolk in baking and catering industry, a fast curing technology with the rational use of egg white is expected.The target of our experiment is to find effective ways to control salted egg yolk filling water, improve sand texture and maintain egg yolk shapes in curing process. Herein, we studied the impact of different metal salts and acids to egg yolk filling water, and found the optimum production condition of salt egg yolk with good sense. The innovation of the experiment was adding salt into "egg white" several times to simulate the penetration of sodium chloride, where "egg white" was taken placed by CMC. The main results were as follows:1. Adding 0.25% ZnCl2,0.75% CaCl2,0.5% C6H5O7Fe·5H2O,0.3% lactic acid, 0.3% citric acid into 20% sodium chloride solution, respectively, we saw that water-filled phenomenon disappeared in citric acid. Besides, hardness of salted egg yolk was greater effected by three kinds of metal salts, and the order was ZnCl2 (187.5-716.9N)> C6H5O7Fe·5H2O (187.5-524.1N)> CaCl2 (187.5-300.6N) Comparing metal salts, citric acid did not play a significant effect on egg yolk hardness, and whitening phenomenon did not exist in yolk surface. So we concluded that the best additive was citric acid.2. Comparing two ways of adding salt, we concluded that sand texture of egg yolk was closely related to permeation rate of sodium chloride. The best optimum process was 4% CMC,0.3% citric acid, and simulation of penetration of sodium chloride to a final concentration of 8% preserved in which the egg yolk was preserved at 60℃in 72 hours. Under the condition, we saw that egg yolk kept a complete shape and the sense score was the most well. In term of analysis results, temperature significantly affected the quality of salted egg yolk; in term of range analysis, the order of factors that impacted the sensory of egg yolk was curing temperature> curing time>pickle concentration. In the 45- 60℃the higher the temperature was, the better the sensory quality was. In addition, the curing time and pickle concentration had no significant effect on the senses (a=0.05); the temperature affected egg yolk oil yield significantly (a=0.05); pickle concentration played an important role of salty (a=0.1).3. With the increase of pickle concentration, egg yolk oil yield relative increased, and was adding salted directly better than simulation of penetration of sodium chloride into egg white to a final concentration of 8%. So we speculated that osmotic pressure had a significant role of oil yield. Color value reflected that with the increase of pickle concentration and preserved time, L and B values of salted egg yolk were on the rise, while A value showed a downward trend. The reasons were that L-value was associated with the precipitation of free fatty acids in egg yolk, and A value decreased due to the dissolution of carotenoids and the increasing of pyrrole pigments concentrations.4. As was shown in SEM, the structure and the tightness of egg yolk particles changed after preserved. On the condition of 14% pickle liquid, particles of the samples preserved with method one were looser and showed a different crystal structure obviously, comparing with those preserved with method two.TEM showed salted egg yolk particles (0.2-2μm in diameter) were smaller than fresh ones (0.8-5μm in diameter), which might be caused by dehydration. From figures we also found that most fat particles were closer together, and their sizes and shapes varied through different treatments. Compared with egg yolk preserved for 48 hours, the white particles (droplets) in egg yolk significantly increased after 96 hours, but the black particles (protein) were on the contrary, where internal particles were larger and looser than external ones.5. After separate curing process, salt content of egg yolk gradually increased with the increase of salt concentration and curing time, which met a sphere penetration model. Besides, with Method One salt content of egg yolk increased faster, and in the outer layer of egg yolk salt content was significantly higher than the center. |
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