There are thousands of nominal reactions in chemistry, but most of them will not say anything to the average person. But there is one reaction that everyone is perfectly familiar with - this is Maillard's reaction. We encounter it when we drink aromatic coffee, eat freshly baked bread and toasted steak. And even when we drink beer with friends. Mayar’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, mud, we will talk about her magic in the kitchen.
First Steak and Anthropogenesis
Zoologists have long noticed that anthropoids prefer thermally processed food over raw. Yes, and all pets are happy to eat human food. Fire, skewers and pans have long become an integral part of human life. And from that very moment, the cultural development of our civilization started. After all, the thermal processing of food sharply increased the efficiency of digestion of food, freeing up time for our ancestors to think and learn about the world. We can say that it was not labor that made us intelligent, but a warm and tasty plate of soup and a steak fried thanks to the chemical reaction of Maillard.
Sugar, fat and protein - meeting in a pan
The composition of food products includes three main components - proteins, fats and carbohydrates (sugars). All of them are important for ensuring human life, but the article is not about that.
Carbohydrates and fats have specific carbonyl groups C = O 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). The composition of proteins includes 20 amino acids, 4 of which (lysine, arginine, tryptophan, histidine) have a free amino group NH 2 and guanidine group C (NH 2 ) 2 , which make them easily vulnerable.
This means that they easily react with the carbonyl group of sugars and fats. It is this reaction of sugar amine condensation that bears the name of Maillard. The reaction proceeds under one condition - the temperature is necessary. And this is exactly what happens on our stove during frying, cooking or baking. It is the “tasty” chemical reaction of Maillard that we owe the appearance of a golden crust on cutlets and buns.
Intricate discovery story
Working on the study of protein synthesis pathways, in 1912, a young Frenchman, doctor and chemist Louis Camill Mayard mixed amino acids and sugars, heated solutions and observed the reaction. Maillard noticed the formation of brown compounds in vitro. 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 noted only their similarity with the humins of the soil.
Scientists S.P. took part in the relay race for determining the Maillard reaction products. Kostychev and V.A. A diamond from Petersburg University (1914) who studied yeast fermentation. But the reaction is not named from the name, because the discoverer did not stop there.
From 1912 to 1913, more than 30 publications and Maillard's doctoral dissertation, “Protein Genesis. The effect of glycerol and sugars on amino acids ”, where the author established several stages in the course of this interaction.
It’s a pity that the scientist didn’t get fame during his life; chemists in 1946 became more interested in the Mayar chemical reaction. It was then that the journal of Agricultural and Food Chemistry published an article by the American chemist John George about the stages and significance of this reaction in cooking. This article on Maillard reaction is today the most cited in the history of the magazine.
But the sugar amine 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 that occur in a pan, in a pan 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, resulting in the formation of acyclic, heterocyclic, polymeric substances. It is they who make the chemical reaction of Maillard “tasty”. They can be colorless and colored, fragrant or with an unpleasant odor. Every housewife knows that it will depend on the cooking conditions.
Caramelization and steak
The complex of reactions discovered by the scientist Maillard is called non-enzymatic boring 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 are still not identified.
Caramelization - the conversion of simple sugars when heated - is not just sweets. This process occurs when grilling meat and frying vegetables. The resulting maltol and isomaltol 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 an increasing number of 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 make sure that the meat is not burnt!
Melanoids have appeared - the reaction has passed
These substances, by their nature irregular polymer formations, have a color from red to dark brown. The structure of many remains a mystery today. We consume up to 10 grams of melanoid per day, which are found in coffee, beer, kvass, wine, bread, fried fish and meat.
Aromatic substances are associated with their formation: 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, immunomodulating properties. They are also capable of binding heavy metal ions.
For example, the antimicrobial effect of the melanoid 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.
Since ancient times, melanoids have been widely used in folk medicine. Remember, all medicinal decoctions on herbs are brown in color and this is due to the presence of precisely these complex chemical compounds in them.
Melanoids are not absorbed in the intestines and are poorly susceptible to enzymatic cleavage. Thus, they perform the function of prebiotics - like dietary fiber, stimulate the growth of bifidobacteria in the intestine.
Is roast harmful?
But there are also disadvantages. Firstly, the Maillard reaction reduces the biological value of proteins that bind to sugars and become less 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 (above 180 ° C) they decompose. And here toxic and carcinogenic substances are formed. It is at these temperatures when frying meat that forms toxic acrylamide. That's why you should not overcook products.