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This article comes from the official account of Wechat: ID:fanpu2019, author: Li Cunpu

Barbecue is a gift from nature to human beings. Chemical reaction is what makes this barbecue perfect.

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The night when human ancestors bid farewell to Ru Mao and drink blood, it must have been due to an unexpected flash of lightning. Lightning struck the thick pine needles of the pine forest and burst into flames. A slightly fat antelope under the tree was trapped by the fire before it could run away, and it was just the right distance from the flame-to borrow a lyrics: a little more from the flame would explode, and a little closer would melt. When the fire faded but still left some warmth, the ancestors picked up the tender leg of lamb inside and took a bite, and the texture and fresh fragrance broke out in the mouth in a beautiful moment, and then decided to go crazy for the barbecue.

Even in modern society, people's diet has long been more colorful than we can imagine, barbecue is still an important choice for business banquets, friends gathering, relatives bragging, couples dating. Barbecue was so obsessive that it triggered a human migration to Shandong in 2023. Small brazier and burrito are very special, but for the body of barbecue, what must be more fascinating is the cooked meat itself.

What is a perfect barbecue? Slightly golden incense skin, rich succulent internal fleshy fibers, full of aroma and grease flavor. It was a wonderful chemical reaction feast, a combination of calories, taste and taste derived from protein, fat, charcoal and seasonings. So how to get a string of barbecue with perfect taste, although it may be a cooking problem or a marketing problem, it should be a chemical problem.

Now, let's cook (now, let's start cooking).

Origin: Maillard reaction, the beginning of flavor and taste, whenever you talk about chemistry and cooking, it must be called Maillard. Although it is a bit of a clich é, academia does not fully understand what the Maillard reaction is. Maillard reaction is named after French physicist and chemist Louis-Camille Maillard (1878-1936). An article published by Maillard in 1912 discussed the related phenomena of brown pigment production on meat surface between 140℃ and 165℃. Although Maillard occupies the right of naming, the chemical reaction mechanism of Maillard reaction was first proposed by American chemist John Edward Hodge (1914-1996) in 1953. The article, entitled "Dehydrated Foods, Chemistry of Browning Reactions in Model Systems (Food dehydration, Browning reaction Chemistry in Model Systems)" was later selected by SCI as a classic citation paper (Citation Classic). Hodge explains the process in which substances such as sugars and amino acids are transformed into melanoids (or Maillard bodies) through a series of reactions.

Melanoid is a series of polymers containing nitrogen, which itself has a scorching taste and taste, while melanoid will split in continuous heating to produce hundreds of small molecular substances with different flavors. these substances containing nitrogen or aromatic ring will become the most attractive components in the barbecue flavor.

Even if we have no intention to delve into the details of the chemical transformation in this paper, we can feel acutely from the transformation route shown in figure 1 that temperature, speed of dehydration, pH value, type of sugar and so on are the keys to regulate the pathway and degree of Maillard reaction.

Fig. 1 Maillard reaction mechanism suggested by Hodge Photo Source: reference [3] Maillard reaction is very rich and competitive with each other, so the practical process of barbecue needs temperature control, thus regulating the path of Maillard reaction, and then obtain different melanin-like melanin and subsequent barbecue flavor. The temperature should not be too high, too high will cause surface carbonization (no one wants to eat meat kebabs that become inorganic), and the temperature should not be too low, which will lead to poor Maillard reaction and poor flavor [4]. Dehydration also affects the final melanoid, and the control of dehydration, on the one hand, can be controlled by temperature, but also by brushing oil to prevent the rapid loss of water and get a different taste. In addition to grease, there are often different seasonings that change the pH value on the surface of the kebabs, which in turn affect the chemical composition of Maillard's products and control the taste details of the final kebabs.

In special barbecues in some areas, barbecue chefs sprinkle sugar on kebabs. Fresh meat is of course nature's best gift, but the addition of extra sugars can control the direction of Maillard's reaction, and the caramelization of sugars (the color of fried sugar in braised meat) can also bring some extra flavor. it is the unconscious use of chemical knowledge by many barbecue stalls.

Photo 2 perfect barbecue, scorched skin and rich succulent internal fleshy fibers. Photo Source: string of Life season 3) continued: heat transfer and water conservation, the warmth between the teeth gave the meat the initial flavor, but this is far from enough to make a perfect barbecue. In fact, although the scorched kebab skin gives the barbecue a full flavor at the entrance, the moment the real teeth are chewed is the beginning of people's calorie intake.

Fig. 3 effect of heating on the particle size of protein assembly structure. A, simulated raw meat; b, 100 ℃ heating 10min; c, 100 ℃ heating 30min. Picture source: reference [5] fresh, tender and succulent, which is the highest evaluation of internal fleshy fiber. If the Maillard reaction on the surface of the kebab is a chemical change at the small molecular level, then the formation of the internal taste of the kebab depends more on the change of the three-dimensional structure of the protein and the retention of moisture. When the protein inside the kebab is heated, the well-assembled protein fiber structure is destroyed-the so-called protein denaturation-thus making the tight protein soft and delicate, while releasing locked water molecules to form gravy. As can be seen from the changes in the protein assembly structure shown in figure 3 [5], as the protein is heated, large aggregates are gradually untied and the proportion decreases gradually, resulting in a smaller protein assembly system-resulting in a more chewable protein taste.

Of course, the protein should not be denatured too much. As shown in figure 4, the protein has a loose structure with no specific orientation before assembly (a), then very tight (b) after assembly, and becomes slightly loose (c) after partial destruction of the assembly structure. Corresponding to the taste of the kebabs, the kebabs are (b) too hard to chew, (c) the roasted ones are just good, and the fibrous chewy ones are soft and juicy, and (a) they often occur in the stew, where the so-called stew is so bad that it melts in the mouth-this is not what the barbecue needs.

Fig. 4 assembly and denaturation of proteins. A, unassembled; b, compact assembly (raw meat); c, assembly partially destroyed (cooked meat) Photo Source: reference [5] of course, the roaster can subtly control the taste of the internal meat. First quickly let the surface of the kebab form a melanin-like polymer layer of Maillard reaction, and then slowly heat the internal protein to denature and produce gravy. Since melanin is a polymer, it can effectively prevent the loss of water from internal gravy and avoid internal meat. The juicy kebabs always have high water content and high specific heat, which can effectively avoid the excessive denaturation of local meat protein and ensure the ultimate taste of the kebabs. In this process, firepower control is very important, but the baker should also multitask-because the internal meat quality produces juice, which is the key to kebab seasoning.

Also at ease: barbecue and health, the aroma that controls fire structure. from a chemical point of view, barbecue produces a lot of nitrogenous organic matter, or aromatic compounds. They are the focus of barbecue flavor, but these substances are often associated with carcinogenics. after all, dioxins and tar may be emerging on the surface of kebabs. What's more, in order to increase flavor, many specialty barbecues are cooked with charcoal fire / fruit tree branches. the spices or organic compounds carried by these natural plants naturally volatilize to the meat surface or provide flavor by direct physical adsorption when burned. or participate in chemical reactions to give fragrance, making kebabs more special, while also bringing new health risks.

Fig. 5 barbecue produces a lot of nitrogen-containing organic matter, which may also be a source of pictures of carcinogens: according to scientific reports, a paper in Nature in 2002 was the first to suggest that at least acrylamide (Acrylamide) would occur in Maillard reaction-or in barbecue [6]. Acrylamide is a well-known potential carcinogen, so eating too much barbecue may increase the risk of cancer. But to put it another way, it doesn't make sense to talk about toxicity, and an occasional barbecue may consume far less toxin than a cigarette of secondhand smoke.

In my mother's opinion, barbecue is a health poison stained with carbon ash; in my opinion, barbecue is a fragrant antidote to depression and anxiety. Of course, although there is nothing that cannot be solved by a barbecue, it seems more important to listen to your mother and not to let her get hurt.

reference

[1] Maillard, L. C.. Action of amino acids on sugars. Formation of melanoidins in a methodical way. Comptes Rendus (in French). (1912), 154: 66-68

[2] Hodge, J. E.. Dehydrated Foods, Chemistry of Browning Reactions in Model Systems. Journal of Agricultural and Food Chemistry. 1953, 1 (15): 92843.

[3] https://zh.wikipedia.org/wiki/%E7%BE%8E%E6%8B%89%E5%BE%B7%E5%8F%8D%E5%BA%94

[4] Van Boekel M. Kinetic aspects of the Maillard reaction: a critical review [J]. Food/Nahrung, 2001, 45 (3): 150,159.

[5] Promeyrat A, Gatellier P, Lebret B, et al. Evaluation of protein aggregation in cooked meat [J]. Food Chemistry, 2010 (2): 412-417.

[6] Stadler R H, Blank I, Varga N, et al. Acrylamide from Maillard reaction products [J]. Nature, 2002, 419 (6906): 449450.

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