At present, the pace of the Spring Festival is getting closer and closer, and the taste of the year is getting stronger and stronger. During the holidays, many people like to treat eggs as a gift. Recently, some netizens found that there was a film on the eggs they bought when they were storing up New Year's goods.
So, what exactly is this membrane? Does it pose a food safety risk? Science and Technology Daily reporter interviewed relevant experts.
The main component of the membrane is liquid paraffin
"Coating is a part of the egg cleaning process. The surface of the eggs from the farm is cleaned and disinfected, and the fresh eggs are then coated. After this process, the eggs are ready for market." Li Liuan, professor of animal science and veterinary medicine College of Tianjin Agricultural University, introduced in an interview with reporters that the reason for coating eggs is mainly to keep fresh.
"An eggshell is not a wall of iron, there are thousands of small holes in the surface." Li Liuan further said that after eggs are stored for a long time, the reason why they become stale is because bacteria, mold and so on enter the egg through the stomata. At the same time, the moisture and air in the egg are discharged through the stomata, which affects the freshness and taste of the egg.
After coating, the egg surface will form a protective film to close the eggshell porosity, inhibit the reproduction of microorganisms on the eggshell surface, prevent microorganisms from invading the egg interior, reduce the evaporation of water in the egg, and ultimately achieve the purpose of extending the shelf life of the egg.
Li said that the operation of coating eggs is simple, can extend the preservation time of eggs at room temperature (25 degrees Celsius under the condition of storage for seven weeks can still be eaten), easy to transport long distances.
This method is cheaper than the refrigerated preservation method used daily, as well as the air-conditioned storage preservation method commonly used in the United States, Australia and other countries.
So, does this film affect food safety? Do we need special treatment for it when we eat it?
"Fresh-keeping coatings that meet national regulations are safe food additives, and consumers do not have to worry." If you're really worried, just wash it off with salt water." Li Liuan introduced that the main component of eggshell preservation coating film is food grade liquid paraffin.
In addition to liquid paraffin, monosaccharide, vegetable oil, petroleum jelly, chitosan, polyvinyl alcohol, propolis and other common food grade coating materials.
"Liquid paraffin has low cost and good film forming effect. Paraffin wax is non-toxic and harmless, and a small amount of oral administration can treat constipation, which is widely used in the food processing industry." Li Liuan said that the "National Standard for Food Safety - Standard for the use of food additives" pointed out that liquid paraffin is a legal food additive, and the maximum use is 5 grams/kg.
There are many ways to keep food fresh
Film preservation is one of the main food preservation methods. In addition to eggs, the preservation method is also applied to fruits and vegetables (citrus, apples, lemons, cucumbers, etc.) and meat products (cold meat, ham, etc.).
"Fruit coating materials are mostly natural, non-toxic and harmless edible chitosan, fruit wax, animal oil, vegetable oil, etc., which is applied to the surface of the fruit by dipping, spraying and other ways to achieve the purpose of preservation." Mr. Lee said.
Food preservation is not only a method of coating preservation, but also the commonly used methods of air conditioning storage preservation, heat treatment preservation, low temperature storage preservation and radiation preservation.
By adjusting the proportion of oxygen, nitrogen and carbon dioxide in the sealed package, the oxygen content in the sealed package is reduced and the carbon dioxide content is increased. "By reducing the oxygen content, you can effectively inhibit microbial reproduction and achieve the purpose of extending shelf life." Mr. Lee said.
Preservation by heat treatment is often used in canning production. This method is to heat the can to a certain temperature by pure physical means, so as to achieve the purpose of killing microorganisms.
Cryogenic storage includes refrigeration and freezing. This method is used to preserve food in refrigerators and freezers. Low temperatures can reduce the reproduction rate of microorganisms in food.
In the environment below 10 degrees Celsius, the reproduction capacity of most microorganisms and spoilage bacteria is greatly weakened; When the temperature drops below zero degrees Celsius, the microbes have basically stopped breaking down the food. When the temperature drops to minus 10 degrees Celsius, most microbes will not survive. Low temperatures can also reduce the activity of some enzymes in food and microorganisms.
In addition, there are radiation preservation methods. The method uses the radiation energy generated by radioactive elements to sterilize and kill fresh meat and its products, grains, fruits, vegetables, seasonings, etc., so as to maximize the shelf life of food.
