Baked lamb skewers, why do I have to go to the store to eat

The following article comes from WeChat public account: Global Science, author Global Science

Picture source: pixabay

The standard in summer is barbecue and beer. How much do you know about barbecue?

Written article | Wang Yibo

Audit | Erqi

Until now, I still remember what Mr. Wu said in high school chemistry teacher: "After learning chemistry, when cooking, vinegar is very accurate."

My level is not enough for precisely vinegar. If you have to find an excuse, when you use liquid in the laboratory, our (standard "operation is to use a straw or pipette, and there will be no such equipment in a" normal "kitchen. However, unknowingly, when I was sprinkled with salt, I would hold the bag in my right hand, and gently knocking my right hand's wrist with my left hand to slowly pour the salt particles from the bag -the habit of weighing powder samples that have been developed over the years It made me almost add more salt and add too much.

These are the small fun in daily life, but the chemical elements in the kitchen are more than that. In the summer, the standard of barbecue and beer will never be outdated. Therefore, let's talk about barbecue today.

Baking with a shelf is better?

In the memory, in the summer, the roadside barbecue is covered with shelves, charcoal fire burning under the shelf, and lamb skewers and steamed buns on it ... while waiting for the lamb skewers, you can also eat cooked edamame and peanuts. Essence At the age of not understanding environmental problems, the scene of the cigarettes on the skewers of the lamb is a beautiful memory of the summer night.

Picture source: pixabay

However, when you walk into a barbecue restaurant, it is likely to encounter a barbecue method called barbecue on paper. It is ignorant and known as environmental protection, but it always has less taste of food grilled with shelf.

If you carefully analyze the process of food cooked, we will find that whether it is a barbecue rack or an electric stove under the barbecue paper, we can heat the food through the ConDuction. From a macro perspective, this is the process of passing the calories to the food by the barbecue rack and electric oven. If you switch to the atomic scale, we will see this picture: the particles in the high temperature barbecue rack or the electric oven run to them and the food and food The interface collides with the particles in low -temperature foods, so that the heat is transferred to the food.

However, the difference is that the charcoal fire under the barbecue can also use another way to provide heat to the food -radiation. Radiation means that the heat spreads outward from the form of electromagnetic waves, and the speed of heat diffusion is proportional to the four squares of the temperature of the Cairvin. Therefore, food can not only obtain calories directly from the barbecue rack, but also the calories radiated by charcoal fire can also effectively heat the food part with a farther food from the shelf. This mixed heating method can increase the level of food flavor and aroma, because all parts of food will be heated to varying degrees. However, the food on the electric oven can only get the heat through contact with the stove directly.

Undoubtedly, the process of food cooked is achieved by obtaining heat. And at such a high temperature, what happened to the food?

What happened between food?

As the temperature rises, the moisture on the surface of the meat will evaporate first, and then the protein and sugar will begin a very critical chemical reaction -Maillard Reaction. In 1912, French chemist Louis-Camille Maillard published an article that for the first time pointed out that amino acids and sugars may have a series of complex processes at high temperatures.

Subsequently, in 1953, an African -American chemist named John Hodge first proposed a model about the Medali reaction. If it was the first time Louis-Camille Maillard discovered the existence of the Marad reaction, then John Hodge was the first person to truly understand the response of Marad.

HODGE believes that the Marada response will go through three stages: in the first stage, the amino reactions of the glutinous rice atmosphere and amino acids to generate glycosylamine; in the second stage, unstable glycosamine will rectify the reaction reaction through a reconstruction reaction reaction. , Generate amino glucose (aminoKetose, has a hydroxyl alchemy); and the last stage covers extremely complicated processes such as reconstruction reactions, conversion reactions, bonus reactions, and polymerization reactions, and produces multiple molecules It includes some molecules responsible for bringing specific flavors, aromas and colors. And this is why it increases the layers of food and aroma. For example, when walking on the road, when the aroma of a ray of bread and coffee comes, most of the mouthful of food aroma is due to the response from the Marad.

Picture source: pixabay

The most afraid of barbecue is to burn, or more precisely, it should be "burned". If it is grilled for too long, the food is exposed to a high temperature environment for a long time, and the substances except carbon except carbon will be volatilized and leaving only the carbon atom, that is, carbonization. However, it is actually a barbecue technique that deliberately exposed food in a short time at high temperature. This can add a little caramel color and smoky flavor. For example, the crispy skin of the food after the food is slightly burnt, and the grilled corn also has different flavors compared to cooking corn. But obviously, the charcoal black left over the head will make the food unable to eat.

Smoky

The cigarettes released by charcoal fire are composed of water vapor, other gases and small solid particles, which will give food more or less smoky flavor. Many of us may prefer this smoky taste.

However, is this smoky taste caused by cigarettes through food?

According to the theory of thermophoresis, the particles migrate from the high temperature area to the low temperature zone. Therefore, the high temperature smoke particles will go to the food that needs to be heated urgently and attach it to the surface of the food, especially the wet surface. To explain this phenomenon, we have to start with the characteristics of water molecules.

In the eyes of chemists, water is composed of a V -shaped structure of water molecules. In each molecule, oxygen atoms are located at the apex, and the two hydrogen atoms occupy the other two positions, and regardless of you and me. It can be seen from this structure that water molecules are a polar molecule. Among them, the oxygen atom is negatively charged and the hydrogen atom is positive. This means that the positive charge of a water molecule will be combined by the negative charge of another water molecule. This conclusion can also expand the combination of other polar molecules.

If this conclusion is brought back to the wet food surface, we will find that the role of more water molecules on the surface of the food is to combine with the water molecules in the smoke particles and other polar molecules to increase the smoky smell of food. Most cigarettes will only stay there (food surface) and will not continue to penetrate into the food.

Pink "smoke rings". Image Source:

https://www.smokedbbqsource.com/sclence-Of-smoke/?utm_source=pinterest&UTM_Medium=social&UTM_CAMPAIGN=SOCIAL- Pugg

However, a small part of the smoke particles still reach the position of about 0.6 cm from the surface of the food. At this time, if the smoke contains nitrogen dioxide or other substances that can be combined with iron in the meat, a pink "smoke ring" will be produced.

However, although the barbecue is fragrant, it should be appropriate. We should have heard that the food after barbecue may contain carcinogens. Some studies have stated that after the meat is treated with high temperature treatment (including fried and bright fire barbecue), heterocytes (HCA) and polygon aromatic hydrocarbons (PAH) will be produced. In the experimental test, both HCA and PAH can increase DNA mutation increases. Risk of cancer. But in terms of specific dosage effects, scientists have no clear answer.

Do you have a plan to eat barbecue?

Reference materials:

https://theconVersation.com/what-makes-smoky-charred-barbecue-taste-So-GOOD-the-Chemistry-COOKING-OPEN-FLAME-184206

https://theconVersation.com/what-makes-smoky-charred-barbecue-taste-So-GOOD-the-Chemistry-COOKING-OPEN-FLAME-184206

https://www.masterClass.com/articleS/charred-food-explaine-IS- IS-difference-Between-and-Burned-Food

https://www.masterClass.com/articleS/charred-food-explaine-IS- IS-difference-Between-and-Burned-Food

https://www.cancer.gov/about-cancer/cauSes-prevention/risk/diet/cooKed-meats-fact-shet

This article is authorized to reprint from WeChat public account: Global Science Author: Wang Yibo

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Reprinted content only represents the author's point of view

It does not represent the high energy office of the Chinese Academy of Sciences

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Edit: Liu Yan

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