Can eggs be kept fresh by coating them?

Can eggs be kept fresh by coating them?


Now, the Spring Festival is getting closer and closer, and the flavor of the New Year is getting stronger and stronger. During holidays, many people like to give eggs as gifts. Recently, when some netizens were stocking up on new year’s goods, they discovered that the eggs they bought had a film on them.

So, what exactly is this membrane? Will it pose a food safety risk? A reporter from Science and Technology Daily interviewed relevant experts.

The main component of the membrane is liquid paraffin

“Coating is a link in the egg cleaning process. Staff will clean and disinfect the surface of eggs from the farm, and then apply film coating to the fresh eggs. After this series of treatments, the eggs can be put on the market.” Li Liuan, a professor at the School of Animal Science and Veterinary Medicine of Tianjin Agricultural University, said in an interview with reporters that the reason why eggs are coated is mainly to preserve their freshness.

“Eggshells are not made of copper and iron. There are tens of thousands of holes on the surface.” Li Liuan further said that the reason why eggs become stale after being stored for a long time is because bacteria, mold, etc. can enter the inside of the eggs through the pores. At the same time, the moisture and gas in the eggs will be discharged through the stomata, thus affecting the freshness and taste of the eggs.

After coating, a protective film will form on the surface of the egg, sealing the pores of the eggshell, inhibiting the reproduction of microorganisms on the surface of the eggshell, preventing microorganisms from invading the inside of the egg, reducing the evaporation of water in the egg, and ultimately extending the shelf life of the egg.

Li Liuan said that coating eggs is easy to operate, and can extend the shelf life of eggs at room temperature (they can still be eaten after 7 weeks of storage at 25 degrees Celsius), making them easier to transport over long distances. This method is cheaper than the daily refrigeration preservation method and the controlled atmosphere storage and preservation method commonly used in the United States, Australia and other countries.

So, will this film affect food safety? Do we need to handle it specially when consuming it?

“Preservation coatings that comply with national regulations are safe food additives. Consumers don’t have to worry. If you really have concerns, just wash them off with salt water.” Li Liuan said that the main component of eggshell preservation coatings is food-grade liquid paraffin. . In addition to liquid paraffin, monoglycerides, vegetable oil, petroleum jelly, chitosan, polyvinyl alcohol, propolis, etc. are also common food-grade coating materials.

“Liquid paraffin has low cost and good film-forming effect. Paraffin is non-toxic and harmless, and can be taken orally in trace amounts to treat constipation. It is widely used in the food processing industry.” Li Liuan said, “National Food Safety Standards – Standards for the Use of Food Additives” pointed out that liquid Paraffin is a legal food additive with a maximum usage level of 5 g/kg.

There are many ways to preserve food

Film preservation is one of the main methods of food preservation. In addition to being applied to eggs, this preservation method is also applied to fruits and vegetables (citrus, apples, lemons, cucumbers, etc.) and meat products (cold fresh meat, ham, etc.).

“Most of the fruit coating materials are natural, non-toxic and harmless edible chitosan, fruit wax, animal oil, vegetable oil, etc., which can be applied to the surface of the fruit by dipping, spraying, etc. to achieve the purpose of preservation.” Li Liuan said.

Food preservation is not just a method of film preservation. Currently, commonly used methods include controlled atmosphere storage, heat treatment, low-temperature storage and radiation preservation.

Controlled atmosphere storage and preservation is to reduce the oxygen content and increase the carbon dioxide content in the sealed packaging by adjusting the ratio of oxygen, nitrogen and carbon dioxide in the sealed packaging. “Reducing the oxygen content can effectively inhibit the reproduction of microorganisms and extend the shelf life.” Li Liuan said.

Heat treatment preservation is often used in canning production. This method uses purely physical means to heat the can to a certain temperature to achieve the purpose of killing microorganisms.

Low-temperature storage and preservation include refrigeration and freezing. Refrigerators and freezers use this method to preserve food. Low temperature can reduce the reproduction rate of microorganisms in food. In an environment below 10 degrees Celsius, the reproduction ability of most microorganisms and spoilage bacteria is greatly weakened; when the temperature drops below zero degrees Celsius, microorganisms have basically stopped decomposing food; when the temperature drops to minus 10 degrees Celsius, most microorganisms Most microorganisms will not survive. Low temperatures can also reduce the activity of some enzymes in food and microorganisms.

In addition, there is also radiation preservation method. This method uses radiant energy generated by radioactive elements to sterilize and kill fresh meat and its products, grains, fruits, vegetables, seasonings, etc., thereby maximizing the shelf life of food.



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