Study On Pickling Dynamics And Quality Evaluation Model Of Preserved Eggs

Preserved eggs is one of traditional unique egg products with special flavor, nutrition and balance of amino acid in China, it is welcomed by consumers at home and abroad. However, the diffusion of curing liquid in curing process and the quality evalution of ripe preserved eggs still depend on experience, which leads to unstable quality. Using duck eggs as raw material, the effects of curing condition on quality of preserved eggs by determining their sensory indicators and physicochemical properties were investigated in this study, and the quality evaluation system of the preserved eggs was built by principal component analysis, and the changes of water content, alkali content, calcium and zinc ion of preserved eggs under curing process were studied, pickling dynamics of preserved eggs has been established. The main research contents and results were as follows:1. Effects of preserved condition on sensory quality, textural properties and chemical compositions of preserved eggs were studied. The flavor, color, chemical compositions of preserved eggs and the textural properties of preserved egg white were influenced significantly by preserved temperature and alkalinity. Higher preserved temperature and alkalinity resulted in higher cohesiveness, lower springiness and chewiness of egg white, and vague egg yolk layer, and stronger astringency and spicy of preserved eggs, but higher free amino acids, soluble protein, calcium and zinc contents of preserved eggs. Lower preserved temperature and alkalinity led to higher springiness, obvious eggs yolk layers, and more fragrance, but appropriate free amino acids, soluble protein, calcium and zinc contents of the preserved eggs.2. The quality evaluation system for the preserved eggs white and yolk was built by the method of principal component analysis. Through principal component analysis, the sensory indicators and physicochemical properties of preserved eggs white were expressed by four principal components, in turn reflecting tastes(pH value and free amino acids), masticatory characteristics(hardness, firmness and chewiness), the contents of calcium and zinc ion, and springiness. The sensory indicators and physicochemical properties of preserved eggs yolk were expressed by four principal components, in turn reflecting color(a* and b*), masticatory characteristics (cohesiveness, firmness and chewiness), springiness and the content of zinc ion. The quality evaluation system for the preserved eggs white and yolk can reflect the quality of preserved eggs, the calculated value was in relatively good agreement with the test value .3. The changes of the contents of water, alkali, calcium and zinc ion of preserved eggs under curing process were studied. The water content of preserved eggs albumen was gradually decreased and finally reached dynamic equilibrium, while the water content of preserved eggs yolk was gradually increased and reached equilibrium state gradually after 30d. The alkali content and zinc ion of preserved eggs were gradually increased and finally reached dynamic equilibrium as well as the zinc ion content of preserved eggs albumen. The trend of zinc ion content of preserved eggs yolk increased firstly and then decreased.4.The pickling dynamic model of preserved eggs were established. The pickling dynamic equation was based on the change law of the contents of water, alkali, calcium and zinc ions of preserved eggs during curing process, the relationship between diffusion coefficient, equilibrium coefficient and preserved conditions was described using quadratic polynomial. The fitting precision of pickling dynamics of preserved eggs was acceptable by verification test. There were differences between the distribution and diffusion velocity of OH^- and Ca²⁺ on the internal preserved eggs, the content of OH" of preserved eggs white was higher than that of preserved eggs yolk, while the content of calcium ion of preserved eggs yolk was higher than that of preserved eggs white. The diffusion velocity of OH^- and Ca²⁺ of preserved eggs white was higher obviously than that of preserved eggs yolk.