The brown crust on the pie is a consequence of the Maillard reaction

Maillard reaction(eng. Maillard reaction) is a chemical reaction between an amino acid and sugar that usually occurs when heated. An example of such a reaction is frying meat or baking bread, where the typical smell, color and taste of cooked food is produced during the heating process. These changes are caused by the formation of products of the Maillard reaction. Together with caramelization, the Maillard reaction is a form of non-enzymatic browning (browning). It is named after the French chemist and physician Louis Camille Maillard, who was one of the first to study the reaction in the 1910s.

Chemistry

The reaction includes several stages:

1. The reactive carbonyl group of the sugar (in its open conformation) interacts with the nucleophilic group of the amino acid to form an unstable N-substituted glycosylamine and water.
2. Glycosylamine is spontaneously rearranged by Amadori and converted to ketosamine
3. Ketosamines in the course of subsequent reactions can turn into

• reductons,
• short-chain hydrolytic products (diacetyl, aspirin, pyruvaldehyde, etc.) or
• brown nitrogenous polymers and melanoidins

Different sugars have different reactivities. The reactivity of the sugars follows in the following order: pentose> hexose> disaccharide. For example, fructose is 100-200 times more active than glucose. The Maillard reaction leads to the formation of numerous products, sometimes with a rather complex and often not yet studied structure.

Industry

The food industry produces many Maillard reaction products that are used to give the desired taste and smell to food.

Medicine

The Maillard reaction does not only occur with food preparation. This reaction between proteins and sugars also takes place in a living organism. Under normal conditions, the reaction rate is so slow that its products have time to be removed. However, with a sharp increase in blood sugar in diabetes, the reaction is significantly accelerated, food accumulates and can cause numerous disorders (for example, hyperlipidemia). This is especially pronounced in the blood, where the level of damaged proteins rises sharply (for example, the concentration of glycated hemoglobin is an indicator of the degree of diabetes). The accumulation of altered proteins in the lens causes severe visual impairment in diabetic patients. The accumulation of some late products of the Maillard reaction, as well as the products of oxidation that occurs with age, leads to age-related changes in tissues. So far, no drugs have been found that can inhibit the Maillard reaction in the body, although some agents (aminoguanidine) significantly reduce the reaction in vitro... The most common late reaction product is carboxymethyl lysine, a lysine derivative. Carboxymethyl lysine in proteins serves as a biomarker of general oxidative stress in the body. It accumulates in tissues with age, such as collagen in the skin, and is elevated in diabetes.

Reaction products

stable, fairly easily determined both experimentally and in real Everyday life patterns reflecting the peculiarities of interpersonal relations in a group and revealing the psychological specifics of those processes, although sometimes in a simplified, schematic form, but meaningfully characterize the main parameters of contact interaction and communication. In socio-psychological science, effects and phenomena are traditionally, although far from always justified, "separate". At the same time, there are practically no more or less meaningful criteria for this differentiation, except for attempts, within the framework of the theory of activity mediation of interpersonal relations, to identify a whole complex of socio-psychological phenomena (reference, the motivational core of interpersonal choices, collectivist identification, collectivist self-determination, attribution of responsibility for successes and failures, etc.), the nature, severity and orientation of which would make it possible to diagnose the level of socio-psychological development of the community, which, in fact, would distinguish the socio-psychological phenomena of interpersonal relations from the complex of socio-psychological effects associated , first of all, with those features of the process of interaction and communication in contact groups, which are determined not so much by the level of development of the latter, as by the specifics of the flow of interpersonal perception in communities of any type. The most famous in socio-psychological science are the boomerang effect, the novelty effect, the halo effect. The psychological essence of the boomerang effect lies in the fact that in a number of cases the efforts of the actor, especially if trust in him is undermined for one reason or another, lead to the exact opposite of the desired result. So, for example, an individual, in whose actions opponents have recognized the motive of manipulation, himself often becomes an object of external manipulation. The psychological essence of the novelty effect lies in the fact that not all information about a social object can be considered as parallel, equivalent. So, if we are talking about a significant communication partner, the first information is remembered as the most important, but at the same time the final information series. As for information about a neutral social object, it is the very first, initial information block that turns out to be decisive in the assessment. The halo effect reflects the existing pattern of interpersonal perception, when, in conditions of an obvious lack of information about a partner in interaction and communication, a general, either negative or positive impression is formed. At the same time, further clarifying information that comes in later is, as a rule, regarded as secondary in comparison with the one that was initially comprehended. In fact, in this case we are talking about stereotyping, about the formation of conservative patterns of perception and assessment of the type of qualities of the “final conclusion”. It is clear that in a number of situations such a simplified approach to assessing the other may turn out to be not only correct, but also a resource-saving way of building an interaction algorithm, and in some cases - erroneous, destructive and therefore destroying the possibilities of establishing productive joint activities. Of course, the list of socio-psychological effects can be significantly expanded, but the above-mentioned effects of interpersonal perception are not only the most elaborated within the framework of socio-psychological science, but are also in their substantive essence, if I may say so, the most ambitious.

A striking manifestation of the boomerang effect is the situation that developed in the USSR in the 70s - 80s. last century. All efforts of Soviet propaganda, in which the confidence of a significant part of the population had already been undermined, to prove the advantages of "developed socialism" over the "decaying West" not only did not achieve the desired goal, but, on the contrary, gave rise to an even more critical attitude towards Soviet reality. Moreover, the effect of the boomerang effect in this situation caused a completely uncritical perception of alternative information broadcast by foreign radio stations. The boomerang effect is also quite common in parent-child relationships, especially during adolescence. Having made sure by this point that the real behavior of parents (as well as other significant adults, for example, teachers) does not always correspond to the norms and principles they declare, many adolescents, especially when faced with a prohibitive influence on their part, exhibit behavioral activity that is directly opposite to the prescribed one. This is especially characteristic of authoritarian and traditionalist families, in which children, upon reaching a certain age, often begin to realize the previously severely suppressed needs for autonomy and the manifestation of initiative in extremely destructive and dangerous forms, such as promiscuous sex life, the use of psychoactive substances, vagrancy, etc. NS.

The effect of novelty, which in the socio-psychological literature is also referred to as the effect of primacy and novelty, has been repeatedly recorded in experimental studies. Thus, in the course of one of the experiments, “a certain stranger was presented to four groups of students, about whom it was said: in the 1st group, that he was an extrovert; in the 2nd group, that he is an introvert; in the 3rd group - first that he is an extrovert, and then that he is an introvert; in the 4th group - the same, but in reverse order. All four groups were asked to describe the stranger in terms of suggested personality traits. In the first two groups, there were no problems with such a description. In the 3rd and 4th groups, the impressions about the stranger exactly corresponded to the order of presentation of the information: the one presented earlier prevailed ”1. A similar result was obtained in one of S. Asch's experiments. One group of subjects was asked to read the phrase: "John is an intelligent, hardworking, impulsive, fastidious, stubborn and envious person", while the other: "John is an envious, stubborn, fastidious, impulsive, hardworking and intelligent person." After that, all subjects were asked to express their general impression of the unfamiliar John. As a result, "... those ... who read adjectives in order from 'intelligent' to 'envious' rated John more positively than those who got the description in reverse order." As noted by GM Andreeva, “this effect was called the“ primacy effect ”and was registered in cases where a stranger is perceived. On the contrary, in situations of perception of a familiar person, there is a “novelty effect”, which consists in the fact that the latter, ie, newer, information turns out to be the most significant ”2.

Note that the effect of primary and newness associated with interpersonal perception should not be confused with the effects of primary and secondary, identified in a number of studies of the communicative process and social influence. In this case, the primacy effect suggests that "other things being equal, the impact of the information presented earlier is usually stronger." In the experiment of N. Miller and D. Campbell, a group of students was asked to read a report on a real trial. At the same time, the experimenters “... put the testimony of witnesses and the arguments of the prosecutor in one volume, and the testimony of witnesses for the defense and the arguments of the lawyer in another. Students read both volumes. A week later, they expressed their opinion, with the majority giving preference to the side with which they were able to get acquainted in the first place. Using an account of a real-life criminal trial, Gary Wells and colleagues found a similar primacy effect by varying the timing of the defense lawyer's opening remarks. His statements were more effective if they were made before the testimony of the prosecution witnesses ”3.

However, in another version of the experiment of N. Miller and D. Campbell, the opposite result was recorded. In a new modification of the experiment, “Miller and Campbell invited another group of students to read one of the volumes of the report. A week later, the researchers gave everyone the opportunity to read the remaining volume and asked the subjects to formulate their opinion immediately. " Now most of the subjects were inclined to the point of view that flowed from the latest information received. This made it possible to conclude that in certain situations there is a secondary effect, which is expressed in the fact that "the latest information received at the time of receipt sometimes has the greatest impact." According to D. Myers, the secondary effect takes place in the presence of two conditions: “1) when two messages are separated by a sufficiently long time; and 2) when the audience makes a decision shortly after the second message. " At the same time, according to D. Myers, “if both messages follow one after the other, and then some time passes, the primacy effect usually takes place” 4.

As for the halo effect, as shown by a number of experimental studies, it “... is most clearly manifested when the perceiver has minimal information about the object of perception, as well as when judgments concern moral qualities. ... In one of the experiments, the assessments of two groups of children, given by the subject of perception, were recorded. One group was made up of “loved ones” and the other was made up of “unloved” children. Although the “loved” (in this case, more attractive) children made (deliberately) mistakes in the performance of the task, and the “unloved” did it correctly, the perceiver attributed positive assessments to “loved ones” and negative ones to “unloved”. ... In another experiment, the transfer of physically attractive traits to the psychological characteristics of the perceived person was demonstrated: a group of men were shown photographs of beautiful, ordinary and clearly ugly women and asked to comment on their features. Only the beautiful were endowed with such traits as sincere, balanced, kind, and even caring and considerate. Thus, the halo effect expresses a tendency to darken certain characteristics and highlight others, plays the role of a kind of filter when “reading” a communication partner ”1.

It must be said that the halo effect is of particular practical importance for social psychologists working with small groups, since it is this effect that significantly enhances the effect of projective identification in the distribution of basic roles at the first stage of group development.

A practical social psychologist, working with a group or organization entrusted to his professional care, must take into account the universal nature of the above-described effects of interpersonal perception and interaction and control not only their specific manifestations within the framework of intragroup activity, but also the very fact of the emergence of these stereotypes and their stabilization in the individual consciousness of members. community, especially if, in his opinion, this affects the nature and intensity of group activity.

The chemical compound that occurs when heated and triggers processes between amino acids and sugar is called the Maillard reaction. It got its name thanks to the French physician Louis Camille Maillard, who investigated this phenomenon.

Often, there is an interaction of elements when frying meat, and can also take place in the process of baking bread products, when, due to heating, a peculiar smell is emitted, an atypical color and taste are formed. All is accompanied by non-enzymatic browning of products. In addition to food, the cause can be an increased glucose content in the human body. The products of the Maillard reaction are the result of the formation of cellular debris, slag that can change the performance of the cell, disrupt its normal functioning.

Formation and course of the reaction

Any change in the cellular formula, constructive composition has its own periods, including the Maillard reaction. The stages are formed sequentially, passing through a certain stage.

Stage one

This is a condensation stage in which the carbonyl group of the sugar reunites with amino acids, causing a chemical reaction with a protein or peptide. As a result of this commonwealth, a substituted aldosylamine begins to form. In simple words, sugar dehydration occurs, in which water is formed. After the Maillard reaction, the structure of the molecules near the oxygen atom begins to change, and the composition rearranges, while intermediate components are formed, which are the cause of the darkening reaction.

Second phase

At this stage, the decomposition and decomposition of the product, which was formed as a result of the Amadori reaction, occurs. Depending on the conditions, the decay can occur in three different ways... Thus, amino acids are degraded by oxidation and by the effects of carbonyl compounds, which are formed from the decomposition of ketosamines. Further, due to the catalization of acids, the decarboxylation process begins, which leads to the release of carbon dioxide, which contributes to the onset of the transamination reaction. This suggests that there is a Maillard reaction. Melanoid formation is confirmed by the appearance of aroma.

Stage three

Polymerization and browning of the product with the formation of a roasted odor. Maillard's reaction at this stage is late, with all the attendant circumstances. Polymerization of reactive elements occurs, which is accompanied by a pungent unpleasant odor. This includes the smell of burnt, rancid, or individual foods such as onions, cabbage, and solvent or acetone, which indicates that a Maillard reaction is taking place.

The product examples are not limited to unpleasant odors, but a pleasant bowel movement can be used when it comes to candy, coffee, or a baked bread crust. The negativity in this case takes place because the use of the ingredients for the consumer is simply unknown.

What the reaction threatens for a person

The fact is that today the food industry uses a huge range of Maillard reaction products in its production. This is necessary to impart a pleasant smell and taste. But the Maillard reaction, in addition to the food industry, can occur in a living human body. When the condition is stabilized, the combination of proteins with sugar is very slow, so the body has time to absorb foods. In the case of an increase in sugar level, acceleration begins, absorption does not occur completely, which leads to the accumulation of toxins that can cause serious diseases. People with diabetes are susceptible to reactions. Therefore, with the Maillard reaction, they may have vision problems, and tissue disorders are also observed.

Changing biomolecules

The Maillard reaction, the formula of which is capable of modifying biomolecules, causes enormous damage to various organs of a functioning organism. This comes from collagen, which is found in tissues, tendons, bones and constitutes a significant amount per body weight. When the structure changes, there is a violation of the tissue component, premature wrinkles may appear, the skin becomes flabby, loses its natural beauty, and this happens earlier than it should be due to age. Therefore, people with diabetes are prone to so-called early aging.

Cooking as the source of the reaction

The Maillard reaction is dominant in cooking because of the many additives and flavors used. Today, chemical food additives are found in almost all food products. But not every supplement can be beneficial for the body, because it is not a natural product, but a particle artificially created from interacting molecules.

The result of eating foods can be a Maillard reaction. The formula depends on the use of substances that are used to obtain an effective product used in the food industry. On the other hand, the result of creation does not differ from that obtained by means of natural components. But the set and arrangement of atoms in industrial manufacture can vary significantly, which makes the food consumed in the end hazardous to health.

The problem is that the industry of flavoring food additives is progressing as quickly as possible, because it is necessary to develop new tastes, aromas that contribute to quick sale, demand among the population, and this may lead to a Maillard reaction. A steak that smells delicious, as if melting in the mouth, attracts a person much more than a piece of homemade cutlet with onions, which is why the population needs to be hooked on such products, which means that the production of flavorings will not be in demand for at least the next decade.

home kitchen

When you cook yourself, there may be a Maillard reaction. Frying meat contributes to the appearance of a certain aroma, specific taste, although the product does not possess these characteristics in its raw state. This is due to the fact that during the interaction of different substances that combine with other elements, all kinds of particles are generated, which have formations of different nature. It is these processes that become the reasons for the pleasant smell. In addition to meat products, this includes coffee, bread, pastries and much more. These reactions are due to the interaction of elements when heated, so the use of products in your own kitchen should be very careful. Non-observance of proportions, excessive addition of flavors, etc. quietly become the causes of the Maillard reaction. Often seasonings, Rollton or Maggi cubes, flavors for different types frying, which are saturated with elements that provoke the occurrence of a reaction. This is used by the food additive manufacturing industry to add a spice to a person through the use of seasonings for cooking.

In addition, such additives are constantly used in cafes, where french fries, steaks, hamburgers, cheeseburgers, etc. are offered in large quantities. This is done so that a pleasant taste and rich smell are constantly beckoning. The human body does not mind after several visits to repeat the use of this food, because addiction begins, and homemade food is no longer so tempting.

How to keep yourself safe

The Maillard reaction does not have a specific model, because many compounds of elements are involved, which contain at least a protein in their composition. In addition, there is no cure for the reaction, there are only some drugs that contain components that can minimize or calm down a change that has already begun for some time. Therefore, to maintain your health, you must first monitor your blood sugar levels. At an older age, undergo examinations to exclude the appearance of diabetes.

It is also worth refusing to visit catering places where the main products are fried food... For home cooking it is worth minimizing the use of flavors and seasonings, giving more preference to steam cooking. It is impossible to completely exclude products containing elements that can provoke the Maillard reaction, because modern industry in this area has captured almost every food industry. It remains only to protect yourself by eating risky products in the least amount.

Kosmachevskaya O.V.

("KhiZh", 2012, No. 2)

PhD in Biological Sciences

Institute of Biochemistry. A.N.Bach RAS

Everyone realizes that normal and wholesome food is food with appetite, food with pleasure; any other food, food by order, by calculation, is already recognized to a greater or lesser extent evil ...

I.P. Pavlov

Chemistry is rich in nominal reactions, there are more than a thousand of them. But most of them will say little to a person far from chemistry, they are for those who understand. However, in this rich list there is one reaction that we all face every day - whenever we come to the stove to prepare something delicious, or drink morning coffee with a sandwich, or beer in the evening with friends. It's about Maillard's reaction, which turns 100 this year. In France, Nancy is even planning a jubilee international symposium on this reaction.

Why such honors? Why is she so remarkable? Yes, because it is ubiquitous and well known to everyone. The formation of humus in soils, coal, peat, sapropel, and therapeutic mud is due to this reaction. But we will talk about much more familiar and attractive things - about the unforgettable aroma of freshly brewed coffee, baked bread and fried meat, about the golden brown crust on a loaf and chop, about the amazing taste of these products. Because all of the above is the result of the Maillard reaction.

First chop and revolution

It is difficult to imagine the life of a modern person without cooking, and cooking without frying, cooking and baking, although all other living things do without heat treatment of food. There is evidence that already Sinanthropus (Homo erectus pekinensis) used fire, and modern Homo sapiens cooked on fire, as they say, from birth. So the love for fried and boiled was formed a long time ago. But what made primitive man put food on fire and then eat it? And why then did everyone start eating processed food?

It is unlikely that we will know when and how it happened. Apparently, for some reason, raw meat got into the fire, fried, and our ancestors simply could not resist not to put fragrant pieces in the mouth. It is clear that fried slice tasted better than raw, even without salt, ketchup and spices. However, this is understandable only to non-biologists. In accordance with the theory of evolution, something should be tasty that is useful, that contains valuable components (an excess of sweet is harmful, but this excess did not threaten our ancestors). Why fried food seems delicious is a non-trivial question. Maybe it’s just because cooked food is easier to digest and taste buds feel it. And soon the cooked food began to be considered sacred, “sanctified by fire,” because during the sacrifice, when potential food was burned on the fire, part of it in the form of smoke was presented as a gift to the gods.

It is interesting that if today's great apes knew how to fry and soar, they would certainly do it. Anthropologists Richard Runham of Harvard and Victoria Wobber of the Max Planck Institute for Evolutionary Anthropology have established that chimpanzees, bonobos, gorillas, and orangutans prefer cooked food raw, be it meat, carrots, or sweet potatoes. What is the matter - the softness of the finished product, its better digestibility or its best taste - is not clear. Although, as we know, pets are also happy to eat "human" food.

One way or another, fire, pans, skewers and pots have become the main tools of cooks and housewives, and delicious warm food is one of the most accessible pleasures. As Jerome K. Jerome wrote, "A clear conscience produces a sense of contentment and happiness, but a full stomach allows you to achieve the same goal with more ease and cost."

However, this method of cooking has generated much more significant, global consequences. There is an interesting theory according to which the heat treatment of food led to an anthropogenetic revolution and served as a starting point in the cultural development of man. Our ancestors were omnivores. This gave an undoubted evolutionary advantage, since the variety of foods consumed was great, but it also had disadvantages: raw, coarse food was poorly digested, so you had to eat a lot, spend a lot of time getting food. Experts have calculated that a chimpanzee spends several hours a day on food consumption, while a modern man spends a little more than an hour (long sitting in restaurants and bars does not count, here most of the time is spent on communication). It turns out that the thermal processing of food, having dramatically increased the efficiency of digestion, reduced the need for resources and gave our ancestors free time and energy that could be spent on thinking, understanding the world, creativity, and creating tools. In other words, cooking gave Homo sapiens the opportunity to become a truly intelligent being.

How sugars, fats and proteins are found in a skillet

One has only to imagine a crispy golden crust on well-done meat or a loaf of fresh bread, and saliva begins to flow. Why is fried food so delicious and attractive to look at?

The three most important components are found in organics used in food: carbohydrates, fats and proteins. I will not dwell on the biological significance of these substances, since this is obvious for the readers of Chemistry and Life. In this case, we will be interested in some of the features of the chemical structure of these substances. Carbohydrates, which are also called natural polyhydroxyaldehydes and polyhydroxyketones with the general formula (CH 2 O) n, contain not only hydroxyl groups -OH, but also carbonyl C = O in their molecules.

In the molecules of natural fats, triglycerides (esters of glycerol and monobasic fatty acids), carbonyl groups are also necessarily present.

Proteins are much more complex, they are polymers, the chains of which are built from a variety of amino acids. The properties of a protein directly depend on which amino acids and in what sequence it is formed. Among the 20 amino acids that make up the protein, there are several that are most chemically vulnerable: lysine, arginine, tryptophan, and histidine. Their molecules contain free amino group (-NH 2), guanidine group (-C (NH 2) 2), indole and imidazole rings.

They are vulnerable because the listed groups, even in the composition of a protein molecule, easily react with the carbonyl group (C = O) of carbohydrates, aldehydes and lipids. (In other amino acids, the amino group reacts only if this amino acid is free or terminal in the polypeptide chain.) elevated temperature, fire or stove. This reaction is known in food chemistry as the sugaramine condensation reaction, or the Maillard reaction.

The story of its discovery is a complicated matter. It is believed that Maillard was the first to discover the active interaction of sugars with amino acids. However, in fairness, it should be noted that for the first time such a reaction was observed by P. Brandes and C. Stoer in 1896, heating sugar with ammonia.

In 1912, a young French physician and chemist, Louis Camille Maillard, began to study the interaction between amino acids and dietary sugars, glucose and fructose. His research was inspired by the desire to find possible pathways for the synthesis of polypeptides. For several hours, he boiled aqueous solutions of sugar or glycerin with amino acids and found that certain complex compounds of a yellow-brown color were formed in the reaction mixture. The scientist mistook them for peptides and hastened to publish the results in the “Compte Rendu de l” Academie des Sciences. ”However, this was the case when the researcher passed off the wishful thinking - a common thing in science. No experimental data confirmed this purely speculative conclusion. To honor Maillard, he understood this, continued his research, and already in the next year, 1913, he discovered a great similarity of the resulting brown pigments with the humic substances of the soil. These were not peptides, but something else.

The baton of research in this direction was picked up by Russian scientists from the laboratory of plant physiology at St. Petersburg University. Soon after Maillard, in 1914, S.P. Kostychev and V.A. Brilliant described the products formed in the reaction between amino acids and sugars in yeast autolysate - the product of self-digestion of yeast cells. Russian scientists have actively investigated the formation of "new nitrogenous compounds" that color the solution dark brown when glucose or sucrose is added to yeast autolysate, and have proven that the material for the synthesis is sugar and amino acids, which easily react without the interference of enzymes.

Of all the researchers involved in this problem, the main results were still obtained by a French scientist who found that the interaction of the keto group (C = O) of the sugar with the amino group (-NH 2) of the amino acid occurs in several stages. Therefore, the sugaramine reaction is known as the Maillard reaction. From 1910 to 1913, the French scientist published about 30 messages, which formed the basis for his doctoral dissertation "The genesis of proteins and organic materials. The action of glycerin and sugars on amino acids ”.

But, as is often the case in science, Maillard's discovery did not receive due recognition during his lifetime. It wasn't until 1946 that scientists again became interested in this reaction. And today we already know a lot about the Maillard reaction. First of all, this is not a single reaction, but a whole complex of processes that proceed sequentially and in parallel without the participation of enzymes and give the reaction mass a brown color. The main thing is that the reaction mixture contains carbonyl groups (in the composition of sugars, aldehydes or fats) and amino groups (proteins). It is clear that such a bouquet of reactions leads to the formation of numerous products of various structures, which in the scientific literature are designated by the term "end products of glycation". This group includes both aliphatic aldehydes and ketones, and heterocyclic derivatives of imidazole, pyrrole and pyrazine. It is these substances - the products of sugaramine condensation - that are responsible for the formation of the color, aroma and taste of thermally processed products. This reaction is accelerated as the temperature rises and therefore is intense during cooking, frying and baking.

Melanoidins: good and evil

The fact that the Maillard reaction has passed can be judged by the golden brown crust on bread, fried fish, meat, by the brown shade of dried fruits. The color of the thermally processed product is given by the dark-colored high-molecular substances melanoidins (from the Greek “melanos”, which means “black”), which are formed at the last stage of the Maillard reaction. However, the color of standard melanoidins is not black, but red-brown or dark brown. Melanoidins only form black pigments, similar to humic substances, if the fire was too strong or if you forgot about fried potatoes, pie in the oven and hopelessly burned them. The very same term "melanoidins" in 1897 was proposed by O. Schmiedeberg. (By the way, "Chemistry and Life" once already addressed the topic of melanoidins; see 1980, No. 3.)

Coffee, cocoa, beer, kvass, dessert wine, bread, fried meat and fish ... While we drink and eat all this, the Maillard reaction and its products, melanoidins, are with us. We consume about 10 grams of melanoidins every day, which is why it is so important to know about their benefits and dangers.

In terms of chemical essence, melanoidins are a wide range of irregular polymers of various structures, including heterocyclic and quinoid structures, with a molecular weight from 0.2 to 100 thousand daltons. The mechanism of their formation is rather complicated and not fully understood - there are too many intermediate products that interact with each other and with the initial substances.

The formation of melanoidins is accompanied by the appearance of many aromatic substances: furfural, oxymethylfurfural, acetaldehyde, formaldehyde, isovaleric aldehyde, methylglyoxal, diacetyl, and others. It is they who give an unforgettable, mouth-watering aroma to freshly baked bread, pilaf, barbecue ... Back in 1948, the founder of our laboratory at the Institute of Biochemistry. A.N.Bakha V.L. Kretovich (later Corresponding Member of RAS) and R.R. Tokarev found that in glucose solutions in the presence of the amino acids leucine and valine, specific tones of the crust are formed rye bread, and in the presence of glycine, a caramel flavor. Isn't it a way to get flavoring and flavoring additives?

Traditional food and beverage recipes include food processing steps that generate melanoidins. For example, dark beers owe their rich color to melanoidinized malt. And flavoring agents and flavorings are ready-made products of the Maillard reaction, which are obtained separately and added to foods and drinks as natural colorings and flavor enhancers. The flavors and condiments for fast food are from the same origin. For example, a brisket-flavored food supplement is produced by microwave drying an enzymatic hydrolyzate of beef meat.

However, the question revolves on the tongue - are these substances dangerous? After all, you just hear: do not eat fried, the crispy crust contains all kinds of carcinogenic rubbish. Let's figure it out.

Today, the scientific literature has accumulated a huge amount of data on the beneficial properties of melanoidins - antioxidant, antimicrobial, immunomodulatory, as well as on their ability to bind heavy metal ions. For the first time, the antioxidant activity of the products of the Maillard reaction was discovered in 1961 in experiments with boiled meat. Then it was shown that cooked meat inhibits lipid peroxidation, and melanoidins and maltol, formed in beef during cooking, act as inhibitors.

Today, scientists studying the nature of the antioxidant activity of melanoidins suggest that it is associated with the structure of these substances, which contain a system of conjugated double bonds in heterocyclic and quinoid units.

It is this structure that allows them to neutralize free radicals and capture metals. And this is extremely beneficial for the body.

For example, by binding iron (Fe 2+), melanoidins prevent it from interacting with hydrogen peroxide in the body to form a strong oxidant and destroyer - a hydroxyl radical (HO.). They can also reduce peroxyl lipid radicals (ROO).

Another advantage is antimicrobial activity. In a recently published article in the journal Food & Function (Ulla Mueller et al. Food & Function., 2011, vol. 2, 265-272), the antimicrobial effect of coffee melanoidins is associated with the formation of hydrogen peroxide (H 2 O 2), which inhibits the growth of Escherichia coli and Listeria innocua bacteria.

Research on coffee melanoidins in recent years has led scientists to believe they may reduce the risk of cancer. In addition, they enhance the synthesis of enzymes of the glutathione-S-transferase family, which detoxify various xenobiotics (Somoza V. et al. "Molecular Nutritin & Food Research" 2005, 49, 663-672). And a group of scientists from Korea, Japan and Germany in experiments on rats showed that the aroma of roasted coffee beans (the result of the Maillard reaction) alters the work of some genes and at the same time proteins are synthesized in the brain that reduce the effects of stress from sleep deprivation. Thus, it is scientifically proven that waking up to the smell of coffee is good for the brain, and therefore pleasant. However, this does not mean at all that coffee should be drunk from morning to evening. Research chief neurologist Yoshinori Masuo of the Health Technology Research Center (Japan) believes that one can simply sniff coffee instead of drinking (Han-Seok Seo et al. Journal of Agriculteral and Food Chemistry. 2008, 56 (12) , 4665-4673).

Thanks to useful properties melanoidins have found applications not only in cooking and food chemistry. In folk medicine, the healing properties of these substances have been used since time immemorial. A decoction of rye ears is used to treat respiratory diseases as an expectorant emollient; barley malt poultices are recommended for skin inflammations and hemorrhoids; decoctions of barley grain treat diseases of the gastrointestinal tract, kidneys, urinary tract and metabolic disorders. In Russia in the 19th century, the so-called hospital kvass was popular, which was included in the diet of every soldier recovering from injury to raise strength. Apparently, this is where the saying “Russian kvass saved a lot of people” comes from.

What about today? External antiseptic for treatment skin diseases- "Mitroshin liquid" - is a concentrate of melanoidins obtained heat treatment oats, wheat and rye. A drug called "Cholef" (Fecholin), a thick extract from wheat germ, is approved for use in the treatment of patients with various forms progressive muscular dystrophy. In the Scientific and Practical Center for Livestock Breeding of the National Academy of Sciences of the Republic of Belarus, we received an experimental batch of the fodder antioxidant additive "Ecolin-1", which is a composition of hydrolysates of malt and peat sprouts. In the Stavropol Polytechnic Institute, the preparation "PV" was made from dairy waste, which is recommended for widespread use in plant growing and animal husbandry as a biostimulator. Unfortunately, all these drugs are produced locally and in small batches.

But back to the melanoidins we eat. They, admittedly, are poorly broken down by digestive enzymes and are not absorbed in the gastrointestinal tract. It would seem a minus? Let's take our time. Melanoidins have the same function as alimentary fiber, improve digestion and stimulate the growth of bifidobacteria, that is, they reveal the properties of prebiotics. And this is rather a plus.

And yet, where does the talk about carcinogens come from? The fact is that at too high temperatures during the Maillard reaction, really toxic or carcinogenic substances can be formed. For example, acrylamide appears when baked or roasted above 180 ° C when melanoidins are thermally decomposed. That's why you shouldn't overcook it. But what's interesting: the researchers found that some products of the Maillard reaction stimulate the formation of enzymes involved in the binding of toxins, including acrylamide. And in model experiments, it was shown that high molecular weight melanoidins inhibit the formation of carcinogenic N-nitrosamines (Kato H et al. Agricultural and Bioljgical Chemistry. 1987, vol. 51).

Of course, the disadvantages can also be attributed to the fact that the Maillard reaction reduces the biological value of proteins, since amino acids, especially lysine, threonine, arginine and methionine, which are most often lacking in the body, after combining with sugars become inaccessible to digestive enzymes and, therefore, are not assimilated. But, you see, it is worth sacrificing a small fraction of amino acids for the sake of an appetizing look, aroma and taste of food. Indeed, without these factors, according to I.P. Pavlov, complete digestion of food is impossible. The food must be delicious!

To assess the harm or benefit of melanoidins, an integrated approach to the problem is required, taking into account all factors and details, often mutually exclusive. This is difficult to do. But there is another way. Today, catalysts and inhibitors have been found for the Maillard reaction, we know how the pH of the environment, temperature, humidity, the ratio of the components on the course of this process and the spectrum of the resulting substances affect. These parameters are usually taken into account in food production. In other words, the Maillard reaction becomes controllable, so it is quite possible to receive in the process culinary processing standard products, only with properties beneficial to the body.

Sunburn, cryptography and shroud

We can meet with the Maillard reaction not only in the kitchen.

If you use self-tanning products (smeared with cream and turned brown without any sun), then you see this reaction on your skin. The active principle of self-tanning is dihydroxyacetone, obtained from sugar beets and sugar cane, as well as by fermentation of glycerin. Dihydroxyacetone or its derivative erythrulose reacts with the amino acids of the proteins of the skin keratin, resulting in the formation of melanoidins, similar to the natural skin pigment - melanin. Within a few hours, as the melanoidins are formed, the skin acquires a natural tan color. This procedure is often used by bodybuilders and fashion models who need to quickly acquire a beautiful skin color.

Unlike sunbathing, self-tanning is believed to produce a naturally brown skin tone without harming your health. However, this is not quite true. Self-tanning has one drawback: it does not protect the skin from UV damage, as natural melanin pigments do. But this is not so bad, the other is worse. Melanoidins are photosensitizers; upon absorption of light, they enter into chemical reactions, in particular, with the formation of a superoxide anion radical (O 2 -). Therefore, the skin covered with melanoidins is more sensitive to the action of sunlight. After 40 minutes in the sun, this skin generates three times more free radicals than untreated skin.

And here is another old application of the Maillard reaction. Remember Mikhail Zoshchenko's children's story "Sometimes you can eat inkwells" about how Lenin, in order to outwit the warders, wrote revolutionary texts on the pages of ordinary fiction books with milk? Milk is a classic invisible (sympathetic) ink. To develop the text written with milk, it is enough to heat the paper with the message over a candle or iron it with an iron. Invisible text will turn visible, brown. What is this if not the Maillard reaction - the interaction of milk proteins with milk sugar lactose! By the way, any available substances containing carbonyl and amine groups, such as saliva, sweat, onion juice, and much more, are suitable for the role of sympathetic ink.

In the Italian city of Turin, in the Cathedral of St. John the Baptist, one of the most revered and mysterious Christian relics is kept - the Turin Shroud, a linen cloth in which, according to legend, Joseph of Arimathea wrapped the body of Jesus Christ after it was taken down from the cross. On this canvas, in an unknown way, the face and body of Christ are captured. The reason for the appearance of a fuzzy yellowish-brown imprint remains a mystery to this day (see: Verkhovsky L.I. "Chemistry and Life", 1991, No. 12; Levshenko M.T. "Chemistry and Life", 2006, No. 7). There are several versions of the chemical reactions that resulted in the image. However, the stumbling block remains the fact that the brown color is only on the surface of the fibers, which remain unpainted inside. It is very likely that we are dealing with a sugaramine reaction.

Chemists Raymond Rogers from the National Laboratory of the University of California at Los Alamos and Anna Arnoldi from the University of Milan tried to experimentally recreate the method of coloring the canvas by means of a sugaramine reaction. Linen fabric was made specially for this experiment according to the technology described 2000 years ago by Pliny the Elder. To carry out the Maillard reaction, as you already know, sugar and amino groups are needed. Where does the sugar come from on the canvas? The fact is that the threads from which the fabric was made were covered with starch, protecting them from damage. The finished tissue was washed in an extract of Saponaria officinalis, which contains saponins - surfactants. They hydrolyze the polysaccharide starch to mono- and oligosaccharides: galactose, glucose, arabinose, xylose, fucose, rhamnose and glucuronic acid. Since the fabric was dried in the sun, the substances from the rinsing water were concentrated on the surface of the fibers.

On the tissue made according to the described technology, the researchers acted with the products of protein decomposition containing amino groups - putrescine (1,4-diaminobutane) and cadaverine (1,5-diaminopentane). Both of these substances are referred to as "cadaveric gases" because they are produced by the decomposition of proteins after death. On the surface of linen fabric, the products of starch hydrolysis interacted with putrescine and cadaverine and a truly surface color was obtained. So Rogers and Arnoldi confirmed the hypothesis about the sugar-amine origin of the image on the shroud and that this reaction could really take place when the body was wrapped in linen cloth of those times.

Melanoidins at the cradle of life

Considering the ease with which the Maillard reaction proceeds, it can be assumed that at the dawn of the emergence of life on Earth, in the prebiotic hydrosphere, that is, in the primary broth, the interaction of sugars with amino acids (aldehydes with amines) was active and everywhere. This, in turn, led to the formation of melanoidin polymers. For the first time the idea that abiogenically formed melanoidins can be the prototype of modern coenzymes was expressed by D. Kenyon and G. Steinman in 1969. And this assumption was not made by chance.

The fact is that the composition of melanoidins includes structures with conjugated double bonds, which impart electron transport properties to polymers. Therefore, melanoidin matrices can mimic some typical biochemical reactions in cells: oxidoreductase, hydrolase, synthase, etc. In addition, these polymers are able to bind heavy metals, which play an important role in the functioning of many enzymes. That is why the formation of such polymers could serve as a starting point in the formation of the main types of biochemical reactions. A. Nissenbaum, D. Kenyon and J. Oro in 1975 hypothesized that melanoidins are protoenzyme systems that played the role of a matrix in the processes of the origin of life before the emergence of systems with a higher specificity.

At the Institute of Biochemistry. A.N. Bach of the Russian Academy of Sciences, employees of the Laboratory of Evolutionary Biochemistry have been modeling the processes of prebiological evolution for many years and studying the role of melanoidin pigments in the complication of carbon-containing compounds. T.A. Telegin and colleagues in these experiments proved that melanoidins have catalytic activity, in particular, they promote the formation of peptide bonds between alanines. Melanoidin pigments were applied to silica gel and placed in a quartz column irradiated with ultraviolet light, through which an alanine solution was circulated. As a result, di-, tri- and tetra-alanine peptides were obtained. Moreover, their concentration was ten times higher than the concentration of dialanin, which was obtained in an experiment with unmodified silica gel. This result showed the advantage of melanoidin matrices over inorganic matrices in the process of abiogenesis.

Maillard reaction and carbonyl stress

Our story about the Maillard reaction and its products would be incomplete if we were silent about the fact that this reaction also occurs in the human body. For the first time, the already mentioned Russian scientists P.A. Kostychev and V.A. Brilliant drew attention to this. Unlike Maillard, they carried out the sugar-amine reaction with more low temperatures, 30-55 ° C, and then it was suggested that it may also occur in cells. This is what they wrote in their article in Izvestia of the Imperial Academy of Sciences in 1916: “Thus, amino acids react with sugar even without the intervention of enzymes. (...) In the current state of science, it would, of course, be completely arbitrary to deny such freely occurring reactions of physiological significance, especially if we take into account that the conditions necessary for the reaction between sugar and amino acids can easily take place in the protoplasm of living cells, since concentrations of the substances participating in the reaction are quite possible there ”.

Indeed, it is now known for certain that this reaction also occurs in the human body, contributing to the development of certain pathologies. Now the attention of researchers is focused on glycation - a non-enzymatic modification of biological macromolecules according to the Maillard reaction, when active carbonyl compounds interact with proteins that accumulate during lipid peroxidation and diabetes.

Due to the accumulation of active carbonyl compounds that occurs with aging or diabetes, so-called carbonyl stress develops. First of all, long-lived proteins suffer, that is, glycate: hemoglobins, albumins, collagen, crystallins, low-density lipoproteins. The consequences are the most unpleasant. For example, glycation of the proteins of the erythrocyte membrane makes it less elastic, more rigid, as a result of which the blood supply to the tissues deteriorates. Due to the glycation of crystallins, the lens becomes cloudy and, as a result, cataracts develop. We can detect proteins modified in this way, which means that they serve as markers of atherosclerosis, diabetes mellitus, neurodegenerative diseases. Today, one of the fractions of glycated hemoglobin (HbA 1c) is one of the main biochemical markers of diabetes and cardiovascular diseases. Reducing the HbA 1c level by 1% reduces the risk of any complications in diabetes by 20%.

In my laboratory, at the Institute of Biochemistry. A.N.Bach, we have developed an experimental system that simulates the conditions of carbonyl stress. We used methylglyoxal as an active carbonyl compound. It turned out that when lysine interacts with methylglyoxal, free radical products are obtained that can reduce oxidized hemoglobin. Due to this, nitric oxide (NO) binds more efficiently with the iron of the heme group, that is, nitrosylation of hemoglobin occurs. In some cases, nitrihemoglobin is formed, and these processes can occur directly in the blood, for example, in diabetic patients. The features of the functioning of such modified hemoglobins have yet to be studied.

By the way, due to the formation of nitrimyoglobin, the so-called nitrite greening of sausages or ham can occur if the technology of processing meat with sodium nitrite is violated ( food supplement E250). Although it is usually added to give meat products an appetizing pink color (not to be confused with the greening caused by the destruction of the heme group as a result of the usual spoilage of the product!).

The story of the Maillard reaction and the melanoidins has come to an end. Although, perhaps, as Kozma Prutkov said, this is the beginning of that end, with which the beginning ends. In the article, only a few strokes indicate the "ubiquity" of the Maillard reaction, but we hope that the reader has a first idea of ​​the importance of the processes occurring between sugars and amino acids in nature.

Another test of our rationality is to ask the same question, formulated in two different but logically identical ways, and see if the same answer will be given to them. Dr. Jones tells his patient John that 10% of people die during elective surgery. Meanwhile, in another office, Dr. Smith tells his patient Joanne that 90% of patients who undergo this operation survive. Given the identity of the information received, will John and Joan agree equally with the operation? If they react like most of the participants in the experiments, John will intuitively feel a great deal of anxiety after he learns that 10% are dying. Even doctors have found that it is better to recommend surgery, after which 93% of patients survive, than one with a mortality rate of 7%.

We've known for a long time that the choice of words in surveys can influence responses. During one vote count, 23% of Americans said the government was spending too much on "helping the poor." However, 53% thought the government was spending too much on social benefits. Most people are positive about "cuts in foreign aid" and increased spending on "relief from hunger in other countries." “Prohibiting something” can be tantamount to “not allowing” it. In 1940, 54% of Americans said we should ban anti-democratic speech, and 75% said we shouldn't allow it. Do these formulations have slightly different nuances of meaning? In recent studies of the "framing effect", words were alternated that were synonymous. Consumers intuitively felt a great deal of sympathy for ground beef leaner by 75% than one that contained 25% fat. People are more surprised when they find out that an event occurs 1 in 20 times than 10 times out of 200, but they are more willing to bet if the odds are 10 out of 100 rather than 1 in 10. Nine out of ten college students believe that a condom effectively protects against HIV infection if the “success rate is 95%”, but only 4 students consider a condom an effective remedy if the “failure rate is 5%”.

Have you noticed how the framing effect affects everyday consumer behavior? Some stores (and most airlines) charge huge markups on their regular prices so that they can offer huge discounts on frequent “sales”. If at store X the price of a CD player has dropped from $ 300 to $ 200, then it seems like a better buy than buying the exact same player in store Y, where it constantly sells for the same price of $ 200. People may agree with a 5% wage hike amid 12% inflation, but protest against a 7% wage cut during zero inflation. My dentist does not charge an additional fee if we pay later; it gives a 5% discount if we pay for the visit immediately and in cash. She's smart enough to know that a fee presented as a possible lost discount is intuitively less annoying than an extra fee, even though it's essentially the same thing.

Our rapidly changing judgments remind us again of the limits of our intuition. Intuitive responses are quick and thrifty, but sometimes irrational. People who understand the power of the framing effect can use it to influence decision making. The young monk received a harsh refusal when he asked if he could smoke while praying. “Ask another question,” a knowledgeable comrade advised him. "Ask if you can pray while you smoke."

Evidence for the Effectiveness of Intuition

• Vision of the blind (responding to visual stimuli in blindness) and prosopagnosia (inability to recognize faces) is the ability of people with brain damage to "see the invisible" when their bodies react to things and faces that are not recognized at the level of consciousness.
• Everyday perception - instant parallel processing and integration of complex information flows.
• Automatic information processing is a cognitive autopilot that basically guides us through life.
• Intuitive learning for young children - teaching the language and the basics of physics.
• Right Brain Thinking - Split-brain people exhibit knowledge that they cannot verbalize.
• Implicit memory is learning how to do something without knowing that you know it.
• Divided attention and priming - automatic processing of information by “basement radar observers”.
• Thin slices - identifying qualities based on observing behavior in just a few seconds.
• Double system of attitudes - since we have two ways of knowing (unconscious and conscious) and two ways of memorizing (implicit and explicit), we react with attitudes on the intuitive (“gut feel”) and rational levels.
• Social and emotional intelligence is an intuitive know-how that allows you to understand and manage yourself in social situations, as well as perceive and express emotions.
• Body wisdom - when an instant response is needed, the emotional pathways of the brain go outside its cortex; sometimes premonitions precede rational understanding.
• Social intuition - our spontaneous inferences about human qualities, moral intuition, infectiousness of mood and accuracy of empathy (sympathy).
• Intuitive experiences are phenomena of unconscious learning, expert learning, implicit understanding, and the extraordinary abilities of our body.
• Creativity (creativity) - at times the spontaneous emergence of new and valuable ideas.
• Heuristics are those mental shortcuts and rules of thumb that usually work just fine.

A dozen intuitive misconceptions

• Memory Construction - Under the influence of our current mood and misinformation, we may form false memories and give questionable testimony.
• Misinterpreting our own mind - often we don't know why we do what we do.
• Misinterpreting Our Own Feelings - We poorly predict the intensity and duration of our own emotions.
• False Predictions of Our Own Behavior - Our intuitive predictions about ourselves are often completely unfounded.
• Distortions of the look back - looking back at events, we proceed from the false premise that we always knew that this was how it would end.
• Defensive Self-Esteem Bias - We exhibit inflated self-esteem in a variety of ways.
• Overconfidence - Our intuitive assessments of our own knowledge are usually less accurate than confident.
• A fundamental attribution error is that we attribute the behavior of others to their tendencies, downplaying the unnoticed circumstances of a situation.
• Persistence of Beliefs and Confirmation Bias - In part because we prefer to corroborate information, beliefs often persist even after their foundations have been discredited.
• Representativeness and Accessibility - A fast and economical heuristic becomes hasty and dirty if it leads us to illogical and incorrect judgments.
• Framing effect - judgments are reversed depending on how the same piece of information is presented.
• Correlation illusion - intuitive perception of connection where it is absent

Strengths and dangers of intuition

We can talk endlessly about the strengths and failures of intuition. But I am sure that these six chapters are enough to confirm two great ideas of modern psychology - that our life is guided to a much greater extent than we realize by "underground" intuitive thinking and that our intuition, although extremely effective with from a performance point of view, it often leads to mistakes that we need to understand. Consequently, intuition - our ability for immediate, direct knowledge prior to rational analysis - has an amazing potential, but at the same time is fraught with amazing dangers. The human mind strikingly demonstrates to us its subtle, indescribable capabilities, as well as the properties that forced Madeleine L'Engle to declare: "The naked mind is an extremely imprecise instrument."

Respecting both the strengths and weaknesses of our inner knowledge, what conclusion should we draw? In forming judgments and drawing conclusions - in business, politics, sports, religion, and other areas of daily life - discerning people listen to their inner voice, but they know when to throw the bridle of rational, reality-based critical thinking over it. Most of the time, our autopilot's perception and intuition is good enough; perhaps they exist only because they helped our ancestors to survive and leave offspring. But in the modern world, accuracy is sometimes of great importance. When it comes down to it, reason should take the reins into its own hands. The Statue of Liberty is holding the torch of the mind. Freedom flourishes in the light of reason.

As we explore popular claims about intuition in sports, professional life, investing, risk assessment, gambling, and spirituality in the next chapter, let us remember one thing: wisdom comes with disillusionment and knowledge. “To free a person from mistakes, one must give, not take away,” Schopenhauer said. "The knowledge that something is false is the truth." In everything from sports to spirituality, separating the strengths of intuition from its weaknesses will prepare us to think and act better.

By comparing our intuition - premonitions, inner voice, and instinctive feeling - with the available evidence, we improve the quality of our thinking.

© D. Myers. Intuition. Opportunities and Dangers. St. Petersburg: Peter, 2010.
© Published with permission of the publisher