In recent years, iron pots seem to have begun to "resurface", and a casual search on the Internet can also find out the various benefits of iron pots. For example, using "frying in iron pots can replenish iron" and "iron pots can be anti-stick without chemical coating, making it safer to use." There are also people who highly praise cast iron pots, believing that "in the past, a cast iron pot could be used well. For decades, the current pot will no longer work for a few years, and it will have to be cast iron pots."

However, an online search revealed that iron pans are divided into cast iron pans, pig iron pans, cooked iron pans, and refined iron pans. The prices also vary from a dozen yuan to several hundred yuan or several thousand yuan. So, what is the difference between these iron pots? Are more expensive iron pots really better than cheaper iron pots?

Picture taken from the Internet

The price of iron pots is not the more expensive the better

Raw materials and processes are the main factors affecting prices

Answer first:The iron pans on the market are mainly divided into two types, namely cast iron pans and cooked iron pans, and these two types of pots are not absolutely good or bad. The prices of different iron pots vary from one to another, mainly due to factors such as differences in production processes, brands and cultural blessings.

** Casting iron pans use iron with relatively high carbon content (i.e. pig iron). ** Such iron pans are often made of melted molten iron directly poured into a mold for casting. The heavy cauldron used on many rural stoves is a cast iron pot.

** Wrought iron is iron with relatively low carbon content. ** Because this kind of iron needed to be forged from pig iron in ancient times, it was also called wrought iron or wrought iron, and refined iron also belongs to wrought iron. The common Zhangqiu iron pot belongs to this category.

source:pixabay

In fact, if you just look at the prices of these two types of pots, you will find that there is no absolute difference between cast iron pots and cooked iron pots. Because they really are not absolutely good or bad.

比如，cast iron pot比较厚重，所以加热这样的锅需要的时间也相对长一些，但它冷却得也比熟铁锅要慢，因此It has better insulation.

Cooked iron pots are generally lighter and lighter than cast iron pots. ** is heated faster and ** is more suitable for stir-frying. Moreover, cooked iron pots are easier to shake than cast iron pots.

But there may be some differences inside the same iron pot. For example, for the same cast iron pot, the raw materials used during pouring, the pouring process, and whether the manufacturer has used the pot in advance will affect the price of the cast iron pot.

In addition, the recommended specification for the cast iron pan industry (QB/T 3648-1999) also mentions the requirements for thermal insulation, impact resistance and burst resistance of cast iron pans. However, because it is a recommended specification, not all cast iron pans will be implemented, and you can also refer to it when purchasing.

It should be noted that because the raw materials of cast iron may contain more impurities, ** When purchasing a cast iron pan, you must check whether you have a quality inspection certificate to ensure health.

The same is true for cooked iron pots. The raw materials used in forging the iron pot, the forging process, and whether the pot is finally roasted blue or otherwise processed will all affect the price of the pot.

Although the price of pots will be affected by many factors, if some iron pots are sold at high prices under the following two names, you have to be careful.

The iron pot really does not replenish iron

Don't spend money to "replenish iron"

说到铁锅，很多人第一反应就是“用铁锅炒菜能补铁”。但其实，铁锅的补铁效果微乎其微，因为Not all types of iron can be effectively absorbed by the body.

There are many types of iron in the foods we eat every day and in iron supplements, but they can be roughly divided into two categories.:Heme iron and non-heme iron.

iron-containing hemoglobin| Wikipedia

Our absorption rate of heme iron is relatively high, reaching 15% to 35%. Usually, duck blood, pig blood, red meat, and iron in animal livers are mainly in this category.

而The absorption rate of non-heme iron is relatively low，比如，有些铁补充剂里的主要成分是硫酸亚铁，它就属于非血红素铁，吸收率就只有 5%到 10%。而许多人以为红枣、菠菜能补铁，但它们里面的铁也是非血红素铁，因此它们的补铁效果不如动物血液。

而The iron scraped off the wok is either iron powder or trivalent iron produced by oxidation of the surface of the wok with air. The absorption and utilization rate of these iron is very low. 比如有人专门研究过人体对铁粉的吸收率，大约只有 1.8%到 3.6%（硫酸亚铁的 36%），因此用铁锅补铁，效果会非常差。

This is actually very abstract. Let's make a mental calculation. If we really use iron pots to replenish iron, how many iron pots will we eat in a year?

According to the Dietary Nutrition Guidelines for Chinese Residents (2016) and the Reference Intakes of Dietary Nutrients for Chinese Residents (Part 3:Trace Elements)(WS/T 578.3-2017), the recommended amount of iron intake for adult men is 12 mg per day and 20 mg per day for women. The recommended amount of iron intake for children varies depending on age and gender, and we can estimate that a family of three needs a daily supplement of 45 mg of iron.

If calculated based on the absorption rate of 3%, about 1500 mg (or 1.5 grams) of iron pan needs to be scraped off every day to meet the demand. Over the course of a year, about 547 grams of iron pots are needed.

也就是说，The iron pot needs to be reduced by more than 1 jin every year. If the iron pot only provides half of the daily iron needs, it will lose half a catty over the course of a year. 另外，我们平时吃的肉类里面血红素铁含量也不低，所以平时吃肉也可以满足我们的基本需求了。

所以，The saying that iron is supplemented by iron pots is not very reliable. 如果有铁锅以此为名义卖高价，就更要小心了。与其花几百几千元买一个“补铁铁锅”，不如多吃一些鸭血，猪肝、蛏子之类的食物。

Iron pan anti-stick without chemical coating

Don't be fooled by the "physical anti-stick" gimmick

In addition, when many merchants promote iron pots, they will mention that their own iron pots are "anti-stick without chemical coating, so they are better than other pots."

In fact, anti-sticking without chemical coating is a common feature of all iron pans and stainless steel pans. ** is not unique to a certain iron pan.

To understand this, let's first talk about why food sticks to the pan.

When we heat food at high temperatures, a series of changes occur in the protein and carbohydrates in the food, and carbohydrates and protein molecules may be destroyed. The part of the protein and sugar close to the pan may form some chemical bonds with the surface of the pan, which is what we often call "sticking to the pan".

To prevent sticking to the pan is to prevent the formation of chemical bonds between the pan and the food.

Non-stick pan anti-stick principle

The non-stick pan with an anti-stick coating uses a material called polytetrafluoroethylene (Teflon). The chemical bonds of this material itself are very "strong" and are not easy to form with protein and sugar molecules in food. New chemical bonds can be anti-stick.

But polytetrafluoroethylene also has some shortcomings. For example, it will begin to deteriorate after heating to 260 degrees Celsius. In most cases, people don't reach such high temperatures when making soups and stir-frying. However, in some special circumstances, such as the water in the pan has boiled dry, or the oil has not been poured after heating the pan for too long, the temperature on the surface of the pan may exceed 260 degrees Celsius.

In addition, if you use a shovel to shovel the pan repeatedly while cooking, or use a steel wire ball when washing the pan, it may also damage the surface of the polytetrafluoroethylene coating and make the non-stick pan ineffective.

Iron pan can also be anti-stick

Of course, chemical coatings are not the only way to prevent sticking.

For example, we usually put some oil into the pan before frying something. Oil can also reduce the formation of chemical bonds between food and the pan. In addition, shaking the pan more when frying food and paying attention to turning the food can also reduce the chance of chemical bonds forming.

此外，还有一些铁锅在制作的时候会进行一项工艺——烤蓝。烤蓝其实就是在锅的表面形成一层致密的四氧化三铁薄膜。这一层膜同样可以起到类似于不粘锅涂层的效果， But oil needs to form an oil film to assist.

leidenfrost effect

还有一点需要说明一下，有些商家可能会声称自己的铁锅既不需要任何涂层，也不需要用油就可以做到防粘，这背后靠的其实是一个叫 The physical principles of the Leidenfrost effect.

The Leidenfrost effect says that when a liquid comes into contact with an object whose temperature is much higher than its boiling point, a thin film will form between the liquid and the surface of the object. For example, when water drops fall on the surface of a very hot pot, the place in contact with the pot will quickly boil and evaporate, forming an "air cushion" to separate the water drops from the pot.

There will be a gap between the water and the surface of the pan| Wikipedia

Using the Leidenfrost effect, any pot can be non-stick.

For example, when frying eggs, as long as you heat the pan first, the temperature of the pan is much higher than the boiling point of water (for example, it reaches 200 degrees Celsius), and then beat the egg. The Leydenfrost effect will appear as soon as the water in the egg touches the bottom of the pot, creating an "air cushion" between the egg and the bottom of the pot. Using this principle, you can really do it without sticking.

But it should be noted that this is not unique to iron pots. All types of pots, aluminum pots, stainless steel pots, and non-stick pots can be done.

Moreover, ** When frying fish and meat, the Leidenfrost effect may fail. ** Because the "air membrane" generated by water vapor may not be able to support the food, the food will still stick to the pan.

Therefore, the iron pan can indeed be anti-stick without coating, but the physical anti-stick of the iron pan still needs to be used in conjunction with oil.

In short, there may be differences in production craftsmanship between iron pots worth tens of yuan and iron pots worth hundreds of yuan, and there are also some brand and cultural blessings, such as "intangible cultural heritage craft iron pots". As long as you can afford to buy a good-looking iron pot, there is nothing wrong with it made purely by hand, but don't be fooled by gimmicks such as "good iron replenishing effect" and "physical anti-sticking".

It is no easy feat implementing digitalization initiatives in industries with many small and medium enterprises (SMEs) like agriculture.

[1]Ems T, St Lucia K, Huecker M R. Biochemistry, iron absorption[J]. 2017.

[2]Hoppe M, Hulthén L, Hallberg L. The relative bioavailability in humans of elemental iron powders for use in food fortification[J]. European Journal of Nutrition, 2006, 45: 37-44.

[3]"Dietary Nutrition Guidelines for Chinese Residents (2016)"

[4]Reference Intakes of Dietary Nutrients for Chinese Residents (Part 3:Trace Elements)"(WS/T 578.3-2017)

[5]https://edu.rsc.org/download?ac=12362

[6]https://www.newscientist.com/article/2266479-physicists-finally-figured- out-why-food-sticks-to-a-frying-pan/

planned and produced

Author 丨 Xiao Wei science creator

Audit 丨 Ji Yang, Researcher at the Institute of Semiconductor, Chinese Academy of Sciences

Planner 丨 Zhong Yanping

Editor in charge 丨 Zhong Yanping

Reviewer 丨 Xu Lai Lin Lin

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