Food Flavors: Benefit or Harm?

In fact, when a person first added fragrant herbs, peppers, cloves or other spices to the meat, he did not do this to give a new taste or aroma. He solved a simple dilemma: either the meat will go bad in a couple of days, or the taste and smell will be spoiled, but the product will last longer. So the first use of natural flavors was associated with a deterioration in natural taste for the sake of shelf life. Later, when the use of spices firmly entered the culture of consumption, the “unnatural" taste and aroma began to seem pleasant to us.

Allylisothiocyanate is the active ingredient in seasonings such as mustard, horseradish and wasabi. They are designed to give food products an uncharacteristic and completely unnatural taste.

With the advent of cooking, we began to deliberately change the taste and aroma of our food for a new, sometimes unpredictable. Spices, and with them in general everything that smells unusual, began to be used as flavorings. The power of entire empires was based on trade in natural flavors - saffron, black pepper, cloves and cinnamon. And it was not at all in search of new lands or knowledge, namely for spices that Vasco da Gama, Columbus and Magellan went on their sea voyages. People added each new open plant with an unusual aroma to their food, not paying attention to the chemical composition (which, by the way, in those days was rather vague).

Much later, the scientific revolution brought an understanding that smell is not some kind of magical substance, but very specific chemicals. They do not have to be grown on plantations in India or the New World. If a plant can synthesize a substance, then what prevents a person from reproducing this process? If the smell of an apple contains a mixture of known compounds, what prevents them from being artificially mixed and getting the same result? Why swim over the seas, be attacked by pirates and competitors if any taste can be literally created in vitro?

Scents of wildlife

The aromas of flowers, berries, fruits, vegetables are so harmonious that sometimes it seems to us that nature created all this especially for us. It is this opinion that underlies many areas of alternative medicine (such as aromatherapy) and our everyday ideas. Meanwhile, this is far from the case.

Any compounds, including those responsible for the smell, the so-called fragrant substances, the plant synthesizes for specific purposes. The products of plant metabolism can be clearly divided into two types. Primary metabolites (proteins, fats, carbohydrates, vitamins) are substances that a plant needs for its vital functions. It is these compounds that make up the nutritional value of our food.


Flavors that are not

Many of the substances that we traditionally take for the aroma of natural tasty and healthy products are not initially present in the plant at all.

So, for example, vanillin, as a separate chemical compound, is simply absent in the pods of a well-known orchid. They synthesize the so-called glucovaniline - a glycoside whose main function is to protect the plant from being eaten by pests. To obtain a fragrant substance with the smell of vanilla, glycoside must also be destroyed, for which a rather complex and lengthy fermentation process is carried out, which leads to a high price. In the food industry, vanillin (much cleaner and much cheaper) is obtained from guaiacol or lignin.

An even more interesting example is mustard, which has learned to defend itself with the help of a powerful chemical weapon - tear allylisothiocyanate (AITC), which is toxic to many living organisms. And since it is also dangerous for mustard itself, the plant does not synthesize it in its finished form, but stores in its tissues two completely harmless separately components: glycosinate sinigrin and the enzyme myrosinase. An animal or insect that decides to feast on a plant damages its tissues, which leads to a mixture of components, while the enzyme (the reaction proceeds in an aqueous medium) “cuts off” glucose from synigrin, forming toxic AITC, or nitrile. Such a feast is expensive for the pest. The same mechanism allows you to "clean" the territory from other plants and microorganisms: in the old and decaying stems and leaves, AITC is formed, "sterilizing" the soil. In a dry mustard powder, there is simply no burning substance, so it acquires a flavor only when water is added, and not immediately (for the same reason, mustard plasters “burn” only after soaking). For the needs of the food industry (for example, for the manufacture of mayonnaise), synthetic AITC is used, which is completely identical to natural.

Secondary metabolites, some of which are aromatic substances, serve completely different purposes. It is traditionally believed that plants have learned to synthesize volatile substances as a result of co-evolution with pollinators or seed carriers. This is only one, and quite a minor side of the issue. The natural aroma contains hundreds of volatile substances, so why should a plant complicate its biochemistry so much? After all, the plant is forced to carry out the synthesis of each compound to the detriment of its development, tearing valuable resources from the production of important products, when one or two varieties of volatile molecules would be enough to attract a pollinator.

When you can't run away

If the primary metabolites of the plant are the very thing for which we eat fruits and vegetables, then the secondary metabolites usually serve the completely opposite purpose - so that the plant is not eaten.

After studying the composition of aroma-forming substances of any flower or fruit, we will find a huge number of compounds with antibacterial and antifungal properties, substances that repel or kill pests (and not only insects). The composition of these aromas is variable. In response to external influences, plants adjust their metabolism, as a result of changing the composition of the smell. In many experiments, it was shown that after damage to the leaf or flower, the resources of the plant are redirected to the synthesis of secondary metabolites. Why? Because in the event of a threat, the plant cannot escape - it switches from growth to protection.

The smell of mowed grass (different from the smell of an untouched lawn) is one example of such a reaction. The substances included in this aroma are secondary metabolites of the plant and are intended to protect against pests that encroach on the juicy flesh, as well as from bacteria and fungi that are greedy for damaged tissues. These same substances are the most important components of the aroma of strawberries or apples.

Among the protection mechanisms, there are more unusual ones. There are many examples of how plants use their fragrances for the enemies of their enemies. Say, as a response to tissue damage, the plant’s caterpillar releases volatile substances that attract parasitic wasps, the natural enemies of the insect. It is also to some extent mutually beneficial cooperation worked out by evolution, but more complex than just plant-pollinator interaction.

Another area of ​​application of aromatic substances is communication. Plants can "communicate" with each other and with other organisms. Not like us, not by sounds and not by signs, the only way available to them is the exchange of molecules. Volatile substances released, for example, when infected with a fungus, signal to nearby relatives about the danger, warning about the proximity of the enemy and causing the metabolism to switch to the synthesis of "antifungal" reagents. And even plants regulate their own vital functions with the help of aromatic substances: plant hormones - volatile molecules - are one of the important components of familiar aromas. Jasmonic acid and its derivatives, which determine the smell of so many colors, are plant hormones.


Non-toxic fragrance

In 1830, amygdalin substance (from the Greek ἀμυγδάλη, almonds) was isolated from the seeds of bitter almonds (Prunus amygdalus var. Amara). Later this compound was found in the bones of plants of the genus plum (Prunus) - apricot, peach, cherry, plum, apples.

Like most other cyanogenic glycosides (glucose compounds), amygdalin is synthesized by the plant as a chemical weapon against enemies. Amygdalin itself is quite harmless, which allows the plant to accumulate it in tissues in significant quantities. However, it is worth the pest to taste the seeds of the plant, the glucosidase enzyme contained in the plant begins to break down amygdalin, resulting in extremely toxic hydrocyanic acid (glucosidase is found not only in the plant, but also in the digestive system of people, birds and insects, so swallowing almonds “doesn’t chewing ”does not save). Once in the body, hydrocyanic acid irreversibly blocks the action of a number of enzymes, which leads to oxygen starvation of tissues, the lethal dose of this substance is 3.7 mg / kg (about 0.3 g for an adult). This amount is contained in less than 100 g of bitter almonds, and for a child only 10 nuts can become fatal.

Amygdalin plays an important role in the formation of almond flavor. The fact is that hydrocyanic acid ... does not smell like almonds! It is on this that the authors of detective stories often determine the cause of poisoning by smell. Benzaldehyde is responsible for the characteristic aroma - a substance formed during the conversion of amygdalin to hydrocyanic acid (however, if a person is poisoned not with hydrocyanic acid but with amygdalin, the smell will really be present). It is benzaldehyde and some other aromatic aldehydes that are used as flavorings with the smell of almonds, apricots, cherries, apples - all those products that contain amygdalin. At the same time, the content of benzaldehyde (fully synthetic) in flavored cookies is much lower than in natural almonds, and there is no poisonous hydrocyanic acid at all.

However, defense mechanisms are not ideal; evolution always finds a vulnerability in them. Worms eat apples, but not because of, but in spite of the presence of substances poisonous to them in them, since they have learned to deal with the protection of fruits. Against the vast majority of others who want to enjoy sweet fruit, this protection remains effective. People eat apples not because of aromatic substances, but because they have sugar and vitamins. The components of aroma bring to our body rather problems. The apple tree’s body spends valuable resources on the synthesis of substances designed to not be eaten, and our body spends its resources on the neutralization of this protection.

Benzaldehyde, formed during the conversion of amygdalin to hydrocyanic acid, is responsible for the characteristic almond flavor. Hydrocyanic acid itself has a completely different smell.

Learn to smell

So why do we like the aromas of the “chemical weapons” of plants? The fact is that our sense of smell is rather cultural than innate. A newborn baby does not distinguish between good or bad smells; for him, they are all fairly neutral. Later, under the influence of training, he begins to associate the smell with other qualities of food: the smell of an orange becomes pleasant because the orange is sweet and tasty, and the smell of rotten fish becomes unpleasant because it can be poisoned.

Smelling training - the process is very flexible and fast. Many traditional dishes of a foreign culture, and simply unexpected combinations of tastes, are perceived as strange and sometimes unpleasant, but a fleeting acquaintance is enough, as this strangeness goes away, and after a while the product is perceived as normal. Our brain quickly builds and destroys the associations between aroma and product. In fact, there is no direct relationship between the smell of a product and its nutritional value. The same aromatic substances can be contained in different products, and the same product can vary greatly in the qualitative and quantitative composition of aromatizing compounds.

Fickle nature

Any aroma, natural or synthetic, is a mixture of fragrant substances. These are the same substances. The difference is that plants synthesize them for their own purposes, and we for their own. For those with whom we add bay leaf to the soup, and to the Borodino bread - coriander seeds. Only when using a natural plant the composition of the mixture is poorly predictable, and in the case of a synthetic aroma we know exactly how many components in it, what they are, what they will turn into during storage and how they will affect the body.

The qualitative and quantitative composition of the synthetic flavor is, of course, different from the composition of the natural product. When creating an apple flavor, all those hundreds of substances found in the apple are not used, and often substances that are not present in the original fruit are often used. But it does not change anything. In addition, the composition of the natural aroma is also unstable, it can vary depending on the degree of maturity of the apple, on the environment, the presence or absence of pests on the plant or nearby and other factors. Even on one apple tree you cannot find two apples that are identical in smell, not to mention the different varieties and that the aroma changes quickly (within minutes) after cutting the fruit.

About the benefits ...

It is believed that a product made using a synthetic flavoring does not bring any benefit. There is one serious logical error in this statement. Flavoring is not a food product. It serves to give flavor, but not nutritional value. The substances in the composition of flavorings can only irritate the receptors in the nose. Various biologically active substances, such as thujone, or coumarin, or safrole (which are part of daily consumed natural products), are not used at all in the production of synthetic flavors because of their potential harm.

Caramel made on natural dyes and flavorings will bring no more benefits than made on synthetic ones. Stewed fruit made from natural fruits and sugar is not more useful than sweet soda with a synthetic flavor (after all, vitamins are not preserved during cooking). The issue of healthy eating is not related to the use of synthetic aromas, obesity and cardiovascular diseases are caused by non-aromatic substances.

... and harm

Can synthetic flavors be harmful? Around this question there are a huge number of myths. The most typical argument of such “horror stories” is that obtaining ultrapure substances is a very expensive process, so flavorings can contain many impurities. In fact, it does not matter at all whether there are impurities in the final product. It is important to know whether they can harm human health. Not only opponents of "chemistry" are thinking about this, seeking to convey the terrible truth to the public.


Flavorists and Perfumers

To create food aromas, more than 4000 individual substances are allowed to use in the world today. However, unlike perfumers, flavorists (specialists in food aromas) are much more limited in their work. Unlike perfumery, in the food industry the principle of upper, middle and lower notes does not work. Instead, the complex aroma is divided into a set of simple ones, called descriptors, from which, as from the constructor, by trial and error, the desired product is assembled. However, this is only the beginning: it is necessary for the flavoring to retain its properties, say, when baking cookies (meanwhile, the temperature in this process may exceed the boiling point of the flavoring components). And after that, the flavoring must retain its properties throughout the entire shelf life of the food product. There are a number of problems associated with the fact that food products are often emulsions (mayonnaise, milk), and flavorings are composed of fat and water soluble components, which leads to an uneven distribution of aroma.

For example, isoamyl acetate, used as a pear flavor and obtained by esterification of isoamyl alcohol and acetic acid, may contain minor impurities of both reagents. However, in fruits containing completely natural isoamyl acetate, these two reagents are also present in the same way. Synthetic vanillin made from guaiacol will contain its admixture. But the same substance is also present in the composition of the natural extract of vanilla, many berries, serves as the main component of natural smoking.

In fact, there are much more impurities in any natural product than in a synthetic one. One can, of course, think that the enzymatic reaction taking place in a living cell selectively leads to the synthesis of a pure substance. Однако стоит учесть, что в клетке одновременно происходит множество реакций, и ароматы компонуются из огромного количества соединений (например, в аромате ананаса их более 900). Так что говорить о селективности в природных процессах можно лишь достаточно условно. Химический синтез в этом отношении гораздо более перспективен: современные методы синтеза позволяют не только селективно получать нужные душистые вещества (как правило, это несложные молекулы), но и контролировать состав примесей. Сложные молекулы, прямой синтез которых затруднен, обычно производятся биотехнологическими методами, и поэтому, согласно пищевому законодательству, считаются совершенно натуральными.

В работе по синтезу пищевых ароматизаторов нет ничего нового — она по сути своей ничем не отличается от работы кулинара, нарезающего яблоко в рыбный салат. В конечном счете каждый вкус и аромат обусловлен конкретными химическими веществами, и для нашего организма не имеет значения, взялись ли они из выращенного на ветке фрукта или из колбы в лаборатории.

Автор статьи — химик, флейворист, руководитель отдела по разработке пищевых ароматизаторов .

Статья «С запахом еды» опубликована в журнале «Популярная механика» (№6, Июнь 2012).

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