Tomatoes are becoming less and less tasty. Is it my illusion? You will understand after reading this!

If you still remember the tomatoes you ate as a child, you may remember that the tomatoes at that time had a particularly strong sweet and sour taste and a soft texture. Eating a tomato in the hot summer is even more refreshing than eating ice cream.

But the tomatoes I bought in the supermarket today, although they looked big and red, seemed to have lost their sweet taste and were hard in the mouth. Have tomatoes really become unpalatable? Or is it just our illusion?

First of all, it is certain that this is not an illusion. Today's tomatoes have indeed become more unpalatable. Why are tomatoes becoming more and more unpalatable? Do we still have the chance to taste the "taste of childhood"?

Today, let’s talk about what tomatoes have experienced in the past.

01

Tomatoes used to be tastier

The fruit pictured below is the currant tomato, the wild ancestor of all tomatoes.

Currant tomato (Solanum pimpinellifolium) is the wild ancestor of all tomatoes. Image source: wikimedia

Currant tomatoes are very small, even smaller than the "cherry tomatoes" we eat today.

Native to western South America, currant tomatoes appeared in Central America south of Mexico about 3,000 years ago, where the Aztecs cultivated the red fruits extensively and used them in a variety of cooking methods.

During the process of widespread cultivation, some mutants of currant tomatoes appeared with larger sizes . After selection and breeding, these larger mutants became the ancestors of modern tomatoes [1].

In the 16th century, after Spanish colonists arrived in America, they also fell in love with this magical little fruit and brought them to Europe. From then on, tomatoes entered the vision of Europeans.

In addition to bringing tomatoes to Europe, Spanish colonists also brought tomatoes to Southeast Asia. In the 16th century, tomatoes were introduced to China from Southeast Asia[2].

But there are still some differences between the tomatoes of four or five hundred years ago and the tomatoes of today. Over the past four or five hundred years, people all over the world have been continuously breeding tomatoes.

By the middle of the 20th century, many varieties of tomatoes had been developed that were sweet and tasty.

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02

Tomato, it's not sweet anymore

Although people have been breeding tomatoes over the past few hundred years, these tomatoes are much tastier than their ancestor, the currant tomato.

But starting in the mid-20th century, the taste of tomatoes began to go downhill again.

Compared with previous tomatoes, the tomatoes we eat today are larger and redder. The selection for these two characteristics, "large" and "red", has affected the sweetness of tomatoes.

Since they are all called tomatoes, let’s talk about red first.

I don't know if you have noticed that in some cities, you can still buy some tomatoes grown by farmers themselves. These tomatoes may still have some green color after the fruits are ripe. Such tomatoes may not look good, but they taste quite sweet.

In fact, before the mid-20th century, it was common for tomatoes to remain slightly green when ripe.

Moreover, these tomatoes often have some green on the shoulder (the end of the fruit) when ripe, and the color is very uneven.

Around 1930, American farmers discovered a mutant tomato strain whose fruits turned red very evenly , and the fruits looked much better than tomatoes that were partially green and red.

Regardless of the taste, a bright red fruit looks sweeter than a green and red fruit. Such tomatoes also look better and soon attracted the attention of tomato merchants.

Through hybridization and breeding, this mutant gene was preserved, and before long, commercial varieties of tomatoes with uneven green and red colors were rarely seen; all were pure red.[3]

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But later science discovered that the bright red tomatoes are not as sweet as the "green-shouldered" tomatoes.

During this selection process, two genes (GLK1 and GLK2) lost their activity.

The gene with the greatest impact is GLK2, which affects the amount of chlorophyll and the formation of thylakoid grana in tomato fruits. As a result, the fruit absorbs less solar energy to generate sugar, and the tomatoes taste less sweet [4, 5].

In addition to red, size also affects sweetness.

In 2017, Chinese and American scientists jointly published a paper in Science.

This study collected 398 tomato varieties, including common commercial varieties on the market, wild varieties, and tomato varieties that have been preserved using traditional planting methods (similar to what the vegetable market owner calls "grown in one's own fields").

The taste, composition and genes of these tomatoes were analyzed, and it was found that the concentration of sugars (mainly glucose and fructose) in tomatoes that determine sweetness is inversely proportional to the size of the tomato.

This is not hard to understand. During the same growth period, the amount of sugar produced is similar, but the larger the tomato grows, the lower the sugar concentration will naturally be[6].

The relationship between the fructose-glucose ratio in tomatoes and fruit size. Image source: Reference [6]

Commercial breeding will select large tomatoes. Big, red tomatoes do look good, but they don’t taste that good.

03

Tomatoes, they are no longer fragrant

In addition to being large and red, tomatoes have become harder and easier to transport and store through generational breeding over more than half a century, but they have become less fragrant.

In the aforementioned Science paper, scientists found that modern commercial tomato varieties have significantly less 13 flavor substances than “homegrown” tomatoes[6].

In addition, a 2010 study found that the loss of flavor substances in tomatoes not only affects their smell, making them less pleasant, but also makes them taste less delicious[7].

So the tomatoes are no longer sweet or fragrant, and of course they no longer have the “taste of childhood.”

04

“The taste of childhood”

Can you come back?

The good news is that scientists have figured out which genes control aroma and sweetness. In addition, during the breeding process, businesses are beginning to focus on taste in addition to appearance and transportation.

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For example, a gene that controls tomato flavor, TomLoxC , had almost disappeared in commercially bred tomatoes, but scientists reintroduced the gene into commercial tomatoes by crossing commercial "farmer-grown" tomatoes with wild currant tomatoes, giving them a flavor boost.

In the past decade, the percentage of commercially bred tomatoes carrying this gene has increased from almost nothing to 5%-6% [8].

In addition, there are also new varieties of tomatoes that are specially bred for delicious taste. However, currently the yield of these varieties is not as large as that of ordinary tomatoes, and they may also have some disadvantages in transportation and storage, so the price will be much higher than ordinary tomatoes.

But I believe that with the joint efforts of geneticists, breeding experts and merchants, we still have hope of enjoying the delicious and inexpensive "taste of childhood".

References:

[1] https://www.smithsonianmag.com/travel/why-wild-tiny-pimp-tomato-so-important-180955911/

[2] Kiple, Kenneth F.; Ornelas, Kriemhild Coneè (2000). The Cambridge World History of Food. Vol. 1. Cambridge University Press.

[3] https://www.npr.org/sections/thesalt/2012/06/28/155917345/how-the-taste-of-tomatoes-went-bad-and-kept-on-going.

[4] Cocaliadis MF, Fernández-Muñoz R, Pons C, et al. Increasing tomato fruit quality by enhancing fruit chloroplast function. A double-edged sword?[J]. Journal of experimental botany, 2013, 65(16): 4589-4598.

[5] Nguyen CV, Vrebalov JT, Gapper NE, et al. Tomato GOLDEN2-LIKE transcription factors reveal molecular gradients that function during fruit development and ripening[J]. The Plant Cell, 2014, 26(2): 585-601.

[6] Tieman D, Zhu G, Resende Jr MFR, et al. A chemical genetic roadmap to improved tomato flavor[J]. Science, 2017, 355(6323): 391-394.

[7] Vogel JT, Tieman DM, Sims CA, et al. Carotenoid content impacts flavor acceptability in tomato (Solanum lycopersicum)[J]. Journal of the Science of Food and Agriculture, 2010, 90(13): 2233-2240.

[8] Gao L, Gonda I, Sun H, et al. The tomato pan-genome uncovers new genes and a rare allele regulating fruit flavor[J]. Nature genetics, 2019, 51(6): 1044-1051.

Author: Science scraps popular science team

Reviewer: Yang Laisheng, Researcher, Lanzhou Academy of Agricultural Sciences

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