Why do store tomatoes have a “cardboard” flavor?
Oddly enough, the main problem that arises when growing tomatoes is their ripening. Simultaneously with the maturation, redness, and the formation of flavoring substances, processes begin to occur that lead to spoilage of the product. The pulp becomes soft, the tomato simply bursts, losing its presentation and creating a breeding ground for mold and other microorganisms. This is a natural course of things, so invented by nature, it is impossible to separate the processes of “ripening” and “spoiling” in time. Therefore, today in stores we see the same "unripe" fruits, the taste of which is sacrificed to the presentation and shelf life, and breeders, displaying the most mature varieties, are forced to destroy their taste.
Why do tomatoes go bad? The fact is that, simultaneously with maturation, a synthesis of an enzyme called polygalacturonase occurs. This enzyme destroys pectin in the cell walls of the tomato, which leads to softening, malformations and all other unpleasant consequences (the plant itself needs this to disperse the seeds).
A little biochemistry
Thus, in order to make tomatoes tasty and still, you need to reduce the concentration of polygalacturonase in them, without changing any other properties. At first glance it seems that this is impossible. However, it is worth remembering how the mechanism of protein synthesis in the cell works.
First, information on the structure of the protein is read from DNA into the chain of messenger RNA, abbreviated mRNA. Then this information in the ribosomes is translated into the finished protein, in our case, into the polygalactonurase molecule. Theoretically, it is possible to reduce the concentration of the enzyme in tomato cells by intervening at any stage in the synthesis process. But it is not so simple. In a living cell, many processes take place simultaneously, and in order not to disrupt the vital activity of the body, any intervention should be very accurate, precise and as selective as possible. We cannot afford to regulate just protein synthesis, we must regulate the synthesis of a very specific protein.
This way exists. For this, a new gene is inserted into the DNA. But not simple, but special. RNA read from this gene is complementary to the original, with which polygalactonurase is synthesized. This type of RNA is often called "antisense". It is able to selectively form a complex with the initial, complementary to it RNA, reducing its concentration. As a result, the rate of synthesis of the enzyme is very much reduced. Manipulations of this kind are selective and do not disrupt the course of other processes in the cell. So, they allow you to change the desired characteristics of the plant, without affecting the rest.
In 1988, a group of researchers from the University of Nottingham (Great Britain) used this method. Together with scientists from the British company Zeneca Seeds, they succeeded in significantly lowering the concentration of polygalacturonase in a tomato by inserting the “antisense” gene described above and thereby achieve a widening of the time interval between the moment of ripening and the loss of presentation. A little later, using the very same method (with slight differences), Calgene, a Californian company, obtained a similar tomato variety, Flavr Savr (pronounced flavor saver, “preserving taste”).
This variety was developed in the UK, where there are restrictions on the cultivation of GM plants, so their production was established in the United States. But they did end up in the United Kingdom - however, already in the form of imported tomato puree (the creators were not able to obtain permission to sell unprocessed tomatoes at that time).
Tomato paste under Safeway and Sainsbury's supermarket brands appeared on the shelves in early 1996. This is not to say that it was a sensation. But it was a success. Losses during harvesting and processing decreased, and the new product was cheaper than traditional tomato paste. The pulp of the new variety was richer in dry matter and pectin than traditional varieties, so the mashed potatoes were 80% more viscous. And, of course, much more delicious. Sales were very active, in many stores overtaking the performance of a "natural" competitor. And the most incredible thing was that on each jar in the most prominent place there was an inscription: “Made from genetically modified tomatoes”, although according to the laws of that time, this was not necessary at all. And none of the buyers was frightened by such an inscription, but quite the contrary.
Nothing boded ill. But the producers of the new tomato puree did not yet know that the famous genetic scientist Professor Arpad Pustai in 1995 began work on assessing the safety of one variety of GM potato, in which the gene responsible for the synthesis of poisonous lectin in the snowdrop was inserted. And no one then could have predicted that this study, or rather, the public resonance around it, would block the path to many good undertakings for a long time.
Safety testing is a standard procedure for any GM plant. If for some reason the new GMO turns out to be harmful, then this is a protection against getting it on the market and a guarantee of the degree of safety that no breeding variety can boast. Even if we do not take into account the inconsistency of the conclusions from the work of Pashtai (he fed GM potatoes with poisonous lectin for grain-eating rats for two weeks, the potato is not included in the usual diet, and then he did not conclude that the potato is harmful to rats, or lectin, or even specific varieties of GM potatoes for mammals, but about the dangers of GMOs in general), nothing extraordinary, in fact, did not happen. More precisely, it would not have happened if the focus of discussion of this work had not shifted, as is often the case, from science to society (and regardless of whether this potato was actually harmful). And society is far from always capable of being guided by facts and not emotions when making decisions. Unfortunately, the role of consumer advocates is most often not the most intelligent representatives of humanity, and almost always do not understand even the basic principles of what they are struggling with.
The beginning of 1999 was marked in the UK (and not only) with daily TV shows and media publications about the dangers of GMOs (something similar can be observed in our country). It was in 1999, according to surveys, that the calmly judicious attitude of Europeans towards GMOs was replaced by a negative one, even irreconcilable. It was then, just three years after such a promising debut, that instead of going further to Europe and possibly reaching us, the first puree from GM tomatoes disappeared from the shelves of Great Britain. Disappeared to never appear again. Together with the mashed potatoes, delicious and unheated tomatoes disappeared. And they’re unlikely to return. The cost of the security check procedure, taking into account the created negative image of GMOs, makes the production of such a product simply unprofitable.
Often we hear that corporations in collusion with the state do not give consumers a choice, they feed us all with GMOs and pesticides. But in fact, it is precisely those who complain about the corporation and the conspiracy that made it so that there are no tasty tomatoes in the stores. Who knows how many more delicious foods we are deprived of by their efforts today?
How to fix a broken
Many probably noticed that “grandmother’s tomatoes”, with characteristic green “immaturities” in the area of the stalk, turn out to be tastier than uniformly red shop fruits. But GMOs have nothing to do with it. Just "grandmother" tomatoes spoil too quickly, and therefore they are not sold in the store. You already know how scientists managed to make tomatoes non-perishable. But the "tastelessness" of modern store tomatoes is due to completely different reasons.
The fact is that photosynthesis in tomatoes is regulated by two genes - GLK1 and GLK2. Their functions overlap, and the breakdown of any of them does not lead to serious violations in the physiology of the plant. Both genes work in leaves. In ripening fruits - only GLK2. Its activity in the region of the stalk is higher, which leads to uneven ripening, when half the fruit is already red and the top is still green.
But over the past 70 years, the efforts of breeders have been directed towards the cultivation of "beautiful" varieties of tomatoes, the fruits of which are painted evenly: presentation, uniform "maturity" are important for mass production. And once during the selection, the GLK2 gene “broke”. Such plants are viable. The fruits of tomatoes with a non-working gene began to stain evenly, and beautiful varieties with this trait quickly captured counters and fields. But at the same time, photosynthesis stopped in the fruits, they became less sugars and aromatic substances: tomatoes lost their real taste.
Recently, a group of scientists from several universities - American (California at Davis, Cornell and Michigan), Spanish (Valencia and Malaga) and the Argentine National University of La Plata - “embedded” in the tomato genome a working version of the once-damaged GLK2 gene and “launched” her. But not only in the area of the peduncle, but evenly throughout the fetus. The results exceeded all expectations: the new tomatoes turned out to be tastier, but the uniformity of color remained. However, we will be honest: we are not sure that the tomatoes really turned out to be tastier, since the conclusions about the taste were not obtained as a result of tasting, but only by chemical analysis. The reason for this is the strict rules: it is impossible to taste prototypes until their safety is verified. And even the developers themselves claim that they have not tried them. We will pretend that we believed them.
But it is significant that genetic engineering was able to fix (and improve) what breeding once ruined. Perhaps when the unreasonable fears created by us around genetic technologies that we created dissipate, buyers will be able to see really tasty fruits in stores, and not just on the pages of scientific periodicals.
Thank you for helping to prepare the material the newspaper “Troitsky Variant - Science” (www.trv-science.ru)The article “The Return of Taste” was published in the journal Popular Mechanics (No. 9, September 2013). Do you like the article?
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