What is food grade stainless steel
Last time I wrote about stainless steel, many partners came to ask me questions about stainless steel health, including:
- 1. Zhao Lu asked: ask Luo Gong. The inner material of the chef’s thermos cup is 403, not 304. Is it safe?
- 2. Kuzai’s hot pot said: May I ask the author, which material is better for tableware in daily life? 304 OK, 410 OK?
- 3. Wat asked: is the stainless steel of 0cr17ni7cu30 the antibacterial stainless steel developed by the Chinese Academy of Sciences? Can it be used as tableware? A tableware bought online before was marked with this. The customer service said it was 304 antibacterial stainless steel. I don’t know much about this. I don’t know if this tableware made of 0cr17ni7cu30 stainless steel will be harmful to your health?
- 4. Caviar said: please ask downstairs. Starbucks cup is made of austenitic stainless steel 06cr19ni10. What is the difference between this material and 304 stainless steel in safety performance? I’m going to give it to a two-year-old. Thank you and look forward to your reply.
- 5. Nini asked: what are the characteristics of 210 stainless steel commonly used on e-commerce platforms? Is it safe to make tableware?
- 6. Roki asked: will 304 and 316L contact coke be corroded?
- 7. Wenhuo qiudao said: is there no big difference between 304 and 410 tableware and kitchenware used in daily environment. Or is it safer and safer to use?
Wait, there are too many questions like this. I only posted some here.
However, through these problems, we can see that we are still very concerned about the health and safety of food contact materials.
In fact, I have answered most of the above questions. I don’t know how to answer one question, so I haven’t answered it for the time being. If you have been studying food contact materials, you can communicate and help more partners.
Aside from these specific problems, today, I would like to take this opportunity to talk about what food grade stainless steel is, how to choose stainless steel tableware, and how to use and maintain them.
What is food grade stainless steel?
Table of Contents
- What is food grade stainless steel?
- Common food grade stainless steel
- Causes of stainless steel tableware rusting
- Advantages and disadvantages of food grade stainless steel tableware
- How to buy Stainless Steel cookers?
- How to maintain stainless steel cookers?
First of all, it is of course stainless steel, there is no doubt about it.
Secondly, in GB4806.9-2016 national food safety standard metal materials and products for food contact, it has been clearly stipulated that food containers can be austenitic stainless steel, duplex stainless steel and ferritic stainless steel. Stainless steel tableware and production equipment can also be made of martensitic stainless steel.
However, what is more important is the migration of harmful elements.
The document stipulates that 4% acetic acid solution (simulated food) is poured into a stainless steel container, boiled for 30 minutes, then placed at room temperature for 24 hours, and then the migration of arsenic, cadmium, lead, chromium, nickel and other elements must be less than a certain value to meet the requirements of food grade stainless steel.
Heavy metals cannot be degraded. After entering the human body, they can interact with proteins and enzymes to make them inactive. They may also accumulate in some organs of the human body and cause chronic poisoning.
I think this is what people are most concerned about.
Let’s take another look at the United States.
For food contact stainless steel, the National Science Foundation (NSF) and the food and Drug Administration (FDA) pointed out that the chromium content in stainless steel materials must be > = 16% in order to be regarded as safe food contact materials.
- FDA＝US Food and Drug Administration
- NSF＝National Science Foundation
Why is it so stipulated?
There are two reasons. First, the chromium content is high and it is not easy to rust. Second, stainless steel has a smooth surface. If the surface is rough, food or liquid may remain, causing bacterial breeding.
Is chromium greater than 16% guaranteed not to release harmful substances?
Of course not.
In fact, although stainless steel is relatively inert than other metals, a small amount of nickel and chromium will still be immersed in food.
The amount of leaching depends on the grade of stainless steel, cooking ingredients, cooking temperature, cooking time, etc.
A small amount of nickel is non-toxic, but people who are sensitive to nickel are in trouble. It usually causes dermatitis.
At the same time, chromium is very important for human health and the metabolism of glucose, protein and fat. Low doses of chromium are good for health, but higher doses may be harmful. The recommended daily intake for adults is 50 to 200 UG, so our body actually needs a small amount of chromium. Most of the chromium we need has been obtained from foods such as broccoli, potatoes, beef, poultry, dairy products and apples.
In general, in a meal cooked with stainless steel, the chromium content exuded into the food is less than 45 micrograms, which is not enough to attract attention, so it can still be used safely.
This means that the stainless steel and other materials used in cooking utensils may be more intact than the stainless steel, so we may get more scratches due to the abuse of chromium, which may be better than the stainless steel.
OK, we just learned about the situation in China and the United States. Now let’s turn our attention to Europe.
At present, there is no unified chromium content standard in Europe. France stipulates that the chromium content of food grade stainless steel is at least 13%, while Italy and Germany have their own standards. However, there are unified standards for metal release.
The European method for testing metal release is to expose stainless steel to citric acid solution (5g / L) with pH value of 2.4 and temperature of 70 ° C for 2 hours, then place it in the environment with temperature of 40 ° C for 24 hours and 238 hours, and then measure the released metal content.
The metal content released shall not be greater than the standard in the figure below.
Metal release standard
Nickel and manganese release, meeting the requirements
Common food grade stainless steel
In stainless steel, chromium and nickel have their own characteristics. Chromium gives stainless steel unique luster and mirror effect. Nickel makes stainless steel stronger and improves its oxidation and corrosion resistance, especially in acidic environment.
According to NSF international standard, stainless steel used in food equipment must be 200，300 or 400 series.
In the 200 series, such as 201 and 202, manufacturers use manganese instead of nickel, which has the advantage of reducing production costs and the disadvantage of becoming more prone to corrosion or rust.
Although this series is also considered as food grade stainless steel, it is not high-quality stainless steel, so my suggestion is that when choosing tableware, it is best not to choose 2 series stainless steel.
304 stainless steel
So far, 304 is the most commonly used stainless steel grade in cooking utensils.
Sometimes, the tableware grading system describes 304 stainless steel as 18 / 8. As you are familiar with, the first number is the percentage of chromium, and the second number is the percentage of nickel, that is, 18 / 8 stainless steel has 18% chromium and 8% nickel.
316 stainless steel
316 type stainless steel with chemical composition of about 16-18% chromium, 10-14% nickel and 2% molybdenum.
The tableware is made of 316 / 18% nickel, also known as 10 / 18% nickel in the grading system.
It is less common than 304 stainless steel. It is a high-end version of stainless steel and is famous for its excellent corrosion resistance. In fact, it is also called marine stainless steel because it is used in the marine environment and can resist salt water erosion. 316 also has many medical uses, such as biomedical implants, so it is also called surgical grade stainless steel.
However, this type of stainless steel is very expensive, so not many cookers are used.
Is 316 surgical stainless steel superior to 304 stainless steel?
In terms of corrosion resistance, yes.
However, in fact, in daily cooking, for any food you want to make, high-quality 304 stainless steel is enough. Unless you want to contain acidic food, 316 stainless steel is usually a better choice.
430 stainless steel
430 is magnetic and nickel free stainless steel. In the tableware grading system, the chromium content of 430 is 18%, and the nickel content is almost 0 (~ 0.75%), so it is called 18 / 0.
Since it does not contain nickel, it is easier to corrode than 304 and 316430 and tends to lose luster slowly.
440 stainless steel
440 and 440C are also common food grade stainless steels. Their main advantage is that they can obtain high material hardness during heat treatment. They are generally used as kitchen knives because they are strong, sharp and can withstand wear.
440 generally do not make tableware and containers, because it is easy to rust compared with 304, 316.
Overall, compared with most other available materials, high-quality stainless steel, whether 304 or 316, is a better choice.
For example, an aluminum pot with a coating will lose its viscosity over time. Teflon coatings will disintegrate if overheated. Glass and ceramic pots have poor thermal conductivity and are easy to break. Copper will react with food, and cast iron needs to be dried, otherwise it will rust.
Considering these factors, stainless steel is popular for its low maintenance, durability and relative inertia.
Based on the understanding of stainless steel, if the tableware rusts, it may be one of the following three reasons:
- 1. Composition of steel: nickel free 18 / 0 stainless steel is easier to rust than 304/316 stainless steel.
- 2. Steel quality: chromium is the key element to make stainless steel stainless. By definition, stainless steel must contain at least 10.5% chromium by weight, and high-quality 304/316 stainless steel must contain 18-20% chromium. Cheaper. Stainless steel without brand may have low chromium content. It’s best not to buy low-cost products. After all, health is more important.
- 3. Too much acidic food, unqualified detergent or extremely salty environment will also lead to stainless steel rust.
Advantages and disadvantages of food grade stainless steel tableware
The biggest disadvantage of stainless steel is poor thermal conductivity. Aluminum or copper core is needed to improve thermal conductivity. In fact, the thermal conductivity of stainless steel is 10 times lower than that of aluminum, which means that the heating time of stainless steel pot is 10 times that of aluminum pot (the thermal conductivity of stainless steel is 10-30 W/M/K and that of aluminum is 237 W/M/K).
Secondly, stainless steel is easy to stick to the pot. If you are not proficient in cooking technology, most food will stick, ha ha.
So why use it? Because stainless steel still has many advantages, it can be said that its shortcomings do not hide its shortcomings.
- 1. It is durable. You can beat, scrape and scrub. It is also much harder than aluminum or copper, and its melting point is much higher than aluminum or copper, which makes it the most durable of all ordinary cooking utensils.
- 2. The appearance is pleasing to the eye. The polished luster of high-quality stainless steel looks very comfortable. Careful observation shows that it is more beautiful than beautiful women.
- 3. Easy to maintain. No special care is needed. If your stainless steel cooker looks old, you can wash it with vinegar or soda to restore luster.
- 4. No chemical reaction. Unlike pure copper and aluminum, which react with acidic food, stainless steel is relatively inert and will not react with food.
- 5. Suitable for high temperature cooking. Stainless steel can withstand high temperature, high heat, no problem.
- 6. Suitable for a wide range of cooking. Stainless steel is very suitable for frying, steaming, frying, boiling, stewing and other cooking methods.
- 7. Value for money. Stainless steel kits are usually reasonably priced and very durable. They are generally used for 10 years, and 8 years is not a problem.
- 8. It can be used in combination with aluminum core or copper core (the aluminum core is deeply buried in two layers of stainless steel). In this way, it can have the advantages of durability, non reactivity of stainless steel and thermal conductivity of other materials.
- 9. Safe cooker option. It is one of the safest cooking utensils on the market.
How to buy Stainless Steel cookers?
1. Stainless steel grade
You should make sure that the cookers are made of 304 stainless steel, because they are the standard configuration of high-quality cookers.
You can see if there is “GB4806.9-2016” on the package. Most cookers will mark these numbers on the bottom or on the packaging box. In order to confirm this, I went to a well-known large supermarket and saw stainless steel pots, stainless steel knives, stainless steel spoons, stainless steel wire leaks, etc. there are indeed “GB4806.9-2016” words, indicating that they meet the national food grade stainless steel standards.
If you can’t find the mark when you choose, you should buy it carefully.
Hold it by hand and feel the weight. Heavier pots need to be made of more materials, which is not easy to produce dents. Of course, this will increase the cost, so it will be more expensive.
If it’s online shopping, you need to check the comments to see if anyone is talking about the weight and firmness of the pot.
3. Core material
Stainless steel is a poor heat conductor. Aluminum or copper core pot can improve heat conduction efficiency, which depends on the thickness of copper core or aluminum core. The thicker the core, the more uniform the heat distribution.
It should be noted that the thickness of the aluminum core must be twice that of the copper core to obtain the same heat distribution, which means that the pot base with aluminum core is thicker than the pot base with copper core.
4. Electromagnetic oven compatibility
The electromagnetic stove uses the principle of magnetic induction, so the cooker must be magnetic.
Stainless steel cookers with high nickel content are not magnetic. Therefore, if you use an induction cooker, you need to buy a stainless steel cooker with low nickel content. For example, look for grades 18 / 4 and 18 / 0. You can conduct a magnet test to check whether the magnet will stick to the side, bottom and inside of the stainless steel cooker. If the pot is magnetic, it has low nickel content.
How to maintain stainless steel cookers?
Compared with coated cookers, the maintenance workload of stainless steel cookers is much less, but attention should be paid to maintenance before they can be used for a long time.
- 1. Cook over medium heat. This helps to reduce food adhesion.
- 2. Take out the food from the stainless steel pot immediately after cooking. Do not use stainless steel for high acid or high salt food, which can prevent corrosion.
- 3. Do not store food in stainless steel pot, especially acidic food (such as tomato based food).
- 4. After cooking, let the pot cool before soaking, because soaking the hot pot with cold water may cause deformation.
- 5. After cooling, wipe the food immediately when preparing for cleaning.
- 6. If there are stains or white deposits on your pot, you can wash it with vinegar and water.
- 7. If food sticks to the pot, soak it for an hour to make it soft. Don’t let the pot soak for too long, which will increase the chance of pitting.
- 8. Do not use abrasive cleaner, cleaning cloth and steel wool to clean it.
- 9. Some stainless steel pots and pans will have aluminum layer. If the outer layer is damaged, the exposure of aluminum layer will lead to aluminum leaching. Therefore, if you use a stainless steel cooker, please pay special attention not to damage its surface.
Source: Network Arrangement – China Flange Manufacturer – Yaang Pipe Industry (www.epowermetals.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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