I'm sure you've all seen leather eggs. Skinned egg is a traditional food in China. It can be eaten directly from the shell or combined with other foods to form a colorful and flavorful cold dish. For example, the cold skin egg tofu, sharp pepper skin egg, skin egg lean pork porridge and so on

Skin egg is also known as changed egg. And because the surface of a pickled egg usually shows a pine-branch pattern, it is also called a pine egg.

What kinds of preserved eggs have you seen? Dirt-covered eggs? Coated eggs? Or vacuum-packed eggs?

Why do they come in packages? Why is the packaging different? What is the purpose of the outer packaging?

The purpose of the different packaging is to preserve the freshness of the eggs. By applying some substances to the eggs, the pores on the surface of the eggs will be closed off, so that the eggs will be in a relatively closed environment. In this state, not only is it difficult for harmful microorganisms to invade the inside of the eggs; and because the pores are closed, the moisture of the eggs will not evaporate seriously because of the pores, thus ensuring the taste of the eggs. Moreover, there is a certain difference between the internal and external alkalinity of the pickled eggs, and when the pickled eggs are finished, the alkalinity will escape from the inside of the pickled eggs to the outside, which will make the pickled eggs deteriorate. Applying some substances on the outside of the eggs can maintain the alkalinity inside the eggs to a certain extent, thus avoiding the deterioration of the eggs.

In the past, clever and industrious people invented the method of coating eggs with mud chaff to solve the problem of preserving eggs. This method is simple and economical, and can also extend the preservation time of the eggs, generally can be saved for about 3 months, but this method is laborious and costly, the workers labor conditions are poor, the consumer consumption is not convenient, and does not meet the requirements of quarantine, sanitation and so on. At the same time the mud bran organization loose, still have the gas and the water will through the skin egg stomata from the loose gap escape; And the mud bran sealing is poor, easy to infect the mold, will lead to the skin egg weightlessness, the flavor drops, the commodity value reduces.

Now popular is the skin egg coating treatment. The use of harmless hydrophobic natural resins and advanced saturated hydrocarbons as the main raw materials prepared from the new coating, coated in the shell of the eggs, has a good closed performance, can prevent the evaporation of water in the eggs, do not make the egg meat loss of water dry shrinkage from the shell variant; at the same time can also stop the air or fungi on the eggs of the invasion.

How are the eggs made?

The most important raw material is, of course, a fresh bird's egg. To make skinny eggs you can use duck eggs, or you can choose eggs, in fact goose, quail and pigeon eggs are also available.

But whichever type of egg you use, it must be a fresh egg, preferably one with a production date of less than a week. Eggs are required to be ovoid, of approximately the same size, of the same species, and with a clean, lubricated, uncracked shell surface.

Then the other accessories are lime and soda ash, tea, salt, and food additives (including food processing aids such as copper sulfate, zinc sulfate), through a certain proportion of the mix, such as 2500g of water, 150g of sodium carbonate, 440g of lime, 80g of salt, 25g of black tea, at the right temperature and the right time, such as 25 degrees Celsius for 30 days, you can harvest! Delicious skin eggs.

Next I come to introduce the role of each auxiliary material of leather eggs

The role of quicklime and soda ash is that quicklime and soda ash react to produce sodium hydroxide, which is also known as caustic soda. The concentration of caustic soda in the pickling liquid plays a decisive role in the production process of leather eggs. Firstly, sodium hydroxide acts on the surface of the eggshell, destroying the protein outer membrane of the eggshell, making the eggshell less strong and the air holes leaky. Secondly, the alkali will make the egg white protein degradation, the generation of peptides and free amino acids, and make the egg white in the ionic bond and hydrogen bonding is greatly reduced, this is the egg white of the clear period, the egg white by the state of the solute into the solution state; after this, the egg white in the hydrophobic force and disulfide bonding increased greatly, this is the egg white of the solidification period, the egg white by the state of the solution into the state of the gel. However, after the formation of the gel in the egg white, not in time to remove the eggs from the lye or terminate the pickling, will allow the PH inside the eggs to further increase, so that the egg white gel deterioration, rotten head or water phenomenon.

The role of salt is mainly to flavor, while it can reduce the pungent flavor of skin eggs, inhibit the growth and reproduction of harmful microorganisms, and also promote egg white coagulation and yolk formation of loose heart. But the dosage can not be too large, otherwise it will be counterproductive

The role of metal salt ions such as divalent copper ions and zinc ions is to form insoluble particles in the late pickling in the eggshell and the inner membrane of the shell, blocking its stomata and pores, and at the same time, repair the corrosion holes produced by the action of the strong alkali, which can effectively limit the processing of late alkali excess penetration into the egg, to avoid the alkali injury, the phenomenon of rotting the head to ensure that the product smoothly turn the color of the maturity

The production of eggs by adding tea to improve the gel hardness, viscosity and color and other qualities of the eggs. The tannins in tea can promote protein coagulation. For example, black tea is often used to increase the color of the eggs, and it also improves the flavor and quality of the eggs

Finally, let's talk about temperature

The higher the temperature, the greater the rate of alkali penetration, which means that the alkali will take a shorter period of time to get inside the eggs. Although the increased rate of alkali penetration will shorten the period of egg white formation, it will easily cause alkali damage to the egg white at a later stage due to the high rate of penetration. The main factor in the formation of egg white color is the pickling temperature. When the temperature is high, the skin egg white color fast, the formation of the skin egg white is reddish brown or brown. If the pickling temperature is low, the color of the egg white will be slow, the formation of the egg white is yellow. The appropriate temperature can promote the alkali fast and stable penetration into the egg, accelerate the coloring of egg white and gel, to maintain its appropriate gel strength. The appropriate temperature is around 25 degrees Celsius

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References:

Study on the effect of different temperatures on the quality of preserved eggs

Analysis of factors affecting the quality of preserved eggs

Progress in the study of the formation of preserved eggs' protein gels and their modulation

The effect of iron, zinc and copper combinations on the quality of preserved eggs

Effect of pickled egg quality on pickling conditions

The effect of pickled eggs' quality on the quality of pickled eggs. Effects of curing conditions on the quality of skin eggs

Analysis of quantitative growth status of Salmonella in skin eggs

Plant-derived coated preserved skin eggs

Research on coated preservative for skin eggs

Study on the effect of heat treatment on improving alkali injury of skin proteins

Effects of CuSO4 on the process of curing skin eggs

Effects of NaOH and temperature on the egg skin egg Effect of NaOH and temperature on the processing of eggs

Effect of different teas and additives on the quality of eggs

Effect of metal salts on the quality of eggs pickled by the clearing method

Analysis of the factors affecting the quality of eggs

Effect of temperature on the quality of eggs in zinc-added process

Production of lead-free eggs by immersion

Processing of eggs and safety of consumption

New type of eggs

Effect of CuSO4 on the improvement of alkalinity injury of skin protein

Improvement and application of a new processing method for leather eggs

Study on the changing law of alkalinity, pH and texture characteristics during the curing process of leather eggs

Changing law of rheological and gel characteristics during the processing of leather eggs

Progress in the study of protein gel formation and its regulation in leather eggs

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