There are thousands of named reactions in chemistry, but most of them won't tell a layman anything. But there is one reaction that everyone is very familiar with, and that is the Maillard reaction. We encounter it when we drink aromatic coffee, eat freshly baked bread and fried steak. And even when we drink beer with friends. Maillard's chemical reaction is the most "delicious", and it is she who makes the food fragrant and beautiful. And although she surrounds us everywhere - the formation of humus, peat, therapeutic mud, we will talk about her magic in the kitchen.
The first steak and anthropogenesis
Zoologists have long noticed that great apes prefer thermally processed food to raw. Yes, and all pets are happy to eat human food. Fire, skewers and pots have long been an integral part of human life. And from that very moment, the cultural formation of our civilization began. After allthermal processing of food dramatically increased the efficiency of food digestion, freeing up time for our ancestors to think and explore the world. It can be said that it was not labor that made us a reasonable person, but a warm and tasty bowl of soup and a steak fried thanks to the chemical Maillard reaction.
Sugar, fat and protein meet in the pan
Food contains three main components - proteins, fats and carbohydrates (sugars). All of them are important for human life support, but this article is not about that.
Carbohydrates and fats have specific C=O carbonyl groups in their chemical structure and, although they have a complex molecular structure, they are generally linear. But proteins are complex molecular compounds, the chains of amino acids in them form complex tertiary and even quaternary formations (globules). Proteins contain 20 amino acids, 4 of which (lysine, arginine, tryptophan, histidine) have free amino group NH2 and guanidine group C(NH2)2 which make them easily vulnerable.
This means that they easily react with the carbonyl group of sugars and fats. It is this saccharoamine condensation reaction that bears Maillard's name. The reaction proceeds under one condition - the temperature is required. And this is exactly what happens on our stove when frying, boiling or baking. It is the “delicious” Maillard chemical reaction that we owe to the appearance of a golden crust on cutlets and buns.
Tangled discovery story
Workingover the study of protein synthesis pathways, in 1912 a young Frenchman, physician and chemist Louis Camille Maillard mixed amino acids and sugars, heated solutions and observed the reaction. Maillard noticed the formation of brown compounds in the test tube. But these were not peptides, but substances that determine the color and smell of ready meals. What kind of substances were formed during the reaction, Maillard did not establish. He only noted their similarity to soil humins.
Scientists S. P. took part in the relay race for determining the products of the Maillard reaction. Kostychev and V. A. Brilliant from Petersburg University (1914), who studied yeast fermentation. But the reaction is not called by name, because the discoverer did not stop there.
From 1912 to 1913, more than 30 publications and Maillard's doctoral dissertation “The Genesis of Proteins. The action of glycerol and sugars on amino acids, where the author established several stages in the course of this interaction.
It's a pity the scientist did not get fame during his lifetime, chemists became interested in the Maillard chemical reaction in more detail in 1946. It was then that the American chemist John George published an article in the Journal of Agricultural and Food Chemistry about the stages and significance of this reaction in cooking. This article on the Maillard reaction is still the most cited article in the journal's history today.
But saccharoamine condensation still proudly bears the name of the French discoverer.
A little chemistry in plain language
Today it is known that the Maillard reaction is a cascade of sequential and parallel reactions thattake place in a frying pan, pot or oven. It all starts with the condensation of sugars (glucose, sucrose and fructose) by the primary amino groups of proteins and peptides. The resulting compounds undergo a series of transformations, as a result of which acyclic, heterocyclic, polymeric substances are formed. It is they who make the chemical Maillard reaction “delicious”. They can be colorless and colored, fragrant or with an unpleasant odor. Every housewife knows that it will depend on the conditions of preparation.
Caramelization and steak
The complex of reactions discovered by the scientist Maillard is called non-enzymatic browning of products with the formation of melanoids (colored substances). The chemistry of the process is complex, hundreds of chemical compounds are formed, most of which have not yet been identified.
Caramelization - the transformation of simple sugars when heated - is not only candy. This process occurs when grilling meat and roasting vegetables. The resulting m altol and isom altol give the smell of baked bread, and 2-H-4-hydroxy-5-methylurethane smells like fried meat.
The cascade of reactions leads to the formation of more and more melanoids and the crust on the steak becomes darker. In water, the Maillard reaction is slower, but in oil and on an open fire, it proceeds quickly. Just be careful not to burn the meat!
Melanoids appeared - the reaction passed
These substances, by their nature, irregular polymeric formations, have a color fromred to dark brown. The structure of many remains a mystery to this day. We consume up to 10 grams of melanoids per day, which are found in coffee, beer, kvass, wine, bread, fried fish and meat.
Associated with their formation are aromatic substances: furfural, acetaldehyde, aldehydes, diacetyl and many others. Food becomes not only beautiful, but also fragrant.
Harm or benefit?
It is with the presence of melanoids that fears about the dangers of fried foods are associated. So are they harmful or not?
A lot of data has been accumulated on the benefits of melanoids, which have antioxidant, antibacterial, immunomodulatory properties. They are also capable of binding heavy metal ions.
For example, the antimicrobial effect of melanoids contained in coffee is associated with the formation of hydrogen peroxide during the Maillard reaction. It is she who inhibits the reproduction and growth of bacteria.
Melanoids have been widely used in folk medicine since ancient times. Remember, all healing herbal decoctions are brown and this is due to the presence of these complex chemical compounds in them.
Melanoids are not absorbed in the intestines and are poorly amenable to enzymatic cleavage. Thus, they perform the function of prebiotics - like dietary fiber, they stimulate the growth of bifidobacteria in the intestine.
Is it bad to eat fried food?
But there are also disadvantages. Firstly, during the Maillard reaction, the biological value of proteins is reduced, which are bound by sugars and becomeless accessible to the enzymes of our body. But isn't it worth the aroma and taste of a steak or a fresh bun?
Secondly, at elevated temperatures (over 180 °C) they decompose. And this is where toxic and carcinogenic substances are formed. It is at these temperatures that meat is fried to produce toxic acrylamide. Here's why you shouldn't overcook your food.
