What is the marble coating, is it harmful to the body?

The non-stick pan is not good if it is coated

In addition to the temperature limit of 250°C or below, the non-stick pan cannot be used to make acidic food. According to investigations, non-stick pans currently on the market are not marked with this restrictive use condition.

The main raw material for non-stick pan coating is polytetrafluoroethylene. On May 1, 1990, the Ministry of Health approved the implementation of the national mandatory standard "Hygienic Standard for Polytetrafluoroethylene Coatings for Food Containers". This standard specifies the sanitary requirements for polytetrafluoroethylene coatings for food containers. "This standard applies to Polytetrafluoroethylene is the main raw material, combined with certain additives to form a polytetrafluoroethylene coating, which is coated on the surface of aluminum, iron plate and other metals. After high temperature sintering, it is used as an anti-stick coating for non-acid food containers. The use temperature is limited. Below 250°C".

Regarding the country’s purpose of formulating this standard, Han Yulian, a researcher from the Standards Division of the Health Supervision Center of the Ministry of Health, who is responsible for interpreting the standard, said affirmatively: “The standard imposes two restrictions on the use of non-stick pans. The second is to limit the use temperature below 250 ℃. The non-stick coating is sintered by PTFE and other additives. This standard is set for testing the quality of the coating, and at the same time, it is limited Conditions are also the limiting conditions when using non-stick pans."

●Why can't non-stick pan make acidic food?

Professor Guan Congsheng, a fluoride expert, deputy secretary-general of the Non-metallic Materials Committee of the Chinese Society for Corrosion and Protection, and director of the Institute of Chemical Engineering of Shandong University, said: "PTFE has a congenital defect, that is, its bonding strength is not high. The non-stick pan is not completely covered with the PTFE coating, and there are always some parts exposed on the metal surface. Acidic substances are easy to corrode the metal body. Once the body is corroded, it will expand, which will expand the coating and cause the coating to fall off in a large area. The relevant standards of the Ministry of Health are formulated based on this principle.” Professor Guan also believes that “the coating is mainly used for anti-sticking, but a thin layer is sprayed, and the combination is not strong. It is definitely not possible to use a shovel to cook vegetables. ."

●Which are acidic foods?

"Acid foods include all kinds of meat, eggs, sugar, rice, etc." Professor Yu Kang, director of the Nutrition Department of Peking Union Medical College Hospital, explained acidic foods. Whether foods are acidic or alkaline is not distinguished by taste, but Use scientific methods to detect the types and quantities of elements contained in food to make judgments. Many foods eaten daily are acidic foods.

●Can all non-stick pans make acidic food?

Wang Fuhui, director of the State Key Laboratory of Metal Corrosion and Protection of the Institute of Metal Research, Chinese Academy of Sciences, said that it depends on the materials used in the pot. The non-stick pans on the market are mainly made of 3 materials: aluminum alloy with a thick layer of aluminum oxide on the surface; stainless steel with a layer of chromium oxide on the surface, which has strong corrosion resistance and slow corrosion; and iron, which is easy to It is corroded by acid in a large area, thus lifting the coating. Wang Fuhui emphasized: “Non-stick pans made of easily corrosive metals such as iron cannot make acidic food. Non-stick pans made of metal with strong corrosion resistance should try not to make acidic food."