Strawberries: A Slightly Different View

Strawberry is a fruit that most people like, not all, and those who don’t like strawberries are a minority, and most often they don’t like them because they are allergic to them. For those of us who love them, April and May are months of pure enjoyment. Of course, we can buy strawberries out of season, but they are strawberries only in appearance, and they taste like Styrofoam and sawdust.

What scientific facts about strawberries should we know?

The plant that produces these fruits is most often a hybrid cultivar from the genus Fragaria, which belongs to the rose family, Rosaceae. The strawberries we buy are usually hybrids of Fragaria x ananassa and have been around in this form since the middle of the 18th century. Before that, the main source of strawberries was the wild strawberry, Fragaria vesca , but although its fruits are extremely fragrant and tasty – it is not very commercially usable because it produces few and small fruits. The forest strawberry is not the ancestor of this local one, with large fruits, as is sometimes mistakenly thought.

 

The forerunner of today’s strawberry varieties originated in France, somewhere in Brittany, as a cross between two New World species: Fragaria virginiana from the east coast of today’s USA and Fragaria chiloensis, a Chilean strawberry. French engineer, soldier, spy Amédée-François Frézier brought 5 specimens of this South American strawberry from South America in 1714. Frézier was both a scientist and a researcher, and it is interesting that his surname is actually derived from fraise , the French word for strawberry.

 

His Chilean strawberries are the ancestors of ours. The fruits of this species are large, fleshy and more similar to the strawberries we buy than our wild strawberries. The Virginia strawberry, Fragaria virginiana , native to North America, including Canada and Alaska, has much smaller fruits and is actually more similar to our wild strawberry.

Just toooo much DNA

The modern strawberry is an octaploid – it has 8 sets of chromosomes. This means that there is a lot of DNA in the strawberry and that is exactly why it is used in biology classes for the DNA extraction experiment. However, these cultivars suffer from a number of flaws – these plants have poor adaptive power, and in fact would hardly survive without our help. That’s why you probably haven’t seen a garden strawberry that went wild and settled in the forest.

By the way, garden strawberries have 7096 genes, and many of them regulate the creation of compounds responsible for the color, size, smell and taste of the strawberry fruit. All strawberries have a haploid set with base 7, that is, their haploid number of chromosomes is 7. As they are octoploids, it means that they have 56 sets of chromosomes, i.e. genes. Our wild strawberry is diploid, which means it has 14 chromosomes. Unfortunately, in crossing and increasing the sets of chromosomes, there was an “exchange of goods”: the fruit increased, but its aroma decreased. That is why cultivated garden strawberries do not smell as intensely as wild, forest ones.

Strawberries are mostly propagated vegetatively, through stolons – heathers, which you can notice if you look at strawberry plantations. In fact, the bulls formed from the stolons are clones of the mother plant.

It should be emphasized that, from the botanical point of view, strawberries are by no means berries and beans: it is a pseudocarp – a false fruit. The fact is that the strawberry is created by the fact that other parts of the flower, not only the carpel, participate in its creation. For example, in a strawberry, the flower lodge turns into a red pseudocarp. Seeds – strawberry achenes are located on the outside of the strawberry, unlike most other fruits, where the seeds are inside. The fleshy part of the strawberry, what we like to eat, is actually a flower bed that has grown.

Biochemistry of color and aroma

The color of most red fruits, as well as the red and purple color of leaves and underground plant parts, is due to the presence of anthocyanins. This is a relatively broad class of organic compounds, water-soluble pigments. Otherwise, anthocyanins change color when the pH value of the environment changes, and they can also be used as pH value indicators. The most common anthocyanins are cyanidin, delphinidin, malvinidin (according to marshmallow), perlargonidin and petunidin. Pelargonidin 3-O-glucoside is a glycosylated anthocyanin that gives strawberries their color. This means that a molecule of pelargonidin is attached to a molecule of one sugar, glucose. To a lesser extent, cyanidin – 3-O-glucoside was also found in strawberries.

Esters, furans and some terpenes are responsible for the aroma of strawberries. Out of about 360 easily volatile substances found in strawberries, about 30 of them are involved in the formation of the distinctive aroma of this fruit. The key molecules of the strawberry aroma are furaneol and methoxyfuraneol, as well as gamma decalactone and methyl anthranilate, which is an ester of anthranilic acid. Furaneol is a derivative of furan, a heterocyclic aromatic compound whose fingers are characterized by the presence of one oxygen atom and 4 carbon atoms. In high concentrations, furan is a carcinogen, but furaneol, which gives aroma to pineapples as well as strawberries, is not. The amount of these substances in the fruit increases as it ripens.

The concentration of sugar in the fruit also increases with ripening. The plant hormone auxin, which is actually indole-3-acetic acid (indole-3-acetic acid) is important for all fruits, not only strawberries. As the amount of sugar increases, the concentration of acids in the fruit, primarily citric acid, decreases.