Source: Bringing Science Home
(Source: Internet)
Written by | Su Chengyu
Proofreading | Skin
In early June, United States woman Kiva bought a big-looking watermelon at a supermarket in Seattle for $8. When she cut the melon and gave it to the children, she found that they only took a bite and stopped eating it, saying that there was a problem with the melon and they couldn't bite it.
Source: TikTok
The mother didn't believe it at first, thinking that it was just an excuse for the child not to eat watermelon. When she took a bite herself, she was surprised to find that the flesh of the watermelon was as hard as rubber.
She took a video and posted it on TikTok.
Source: TikTok
In the video, Kiva shows how she breaks a watermelon slice with a lot of force, but it takes some force to break it like elastic rubber. She questioned, "What are these watermelons made of?" The video quickly went viral on TikTok, attracting millions of views and comments.
United States who say watermelons are fake at every turn Source: TikTok
With the increase in speculation and conspiracy theories, some netizens began to question the food safety of United States, believing that the food United States may be being replaced by prop food.
"Rubber" avocado on TikTok Source: TikTok
A few days later, another TikTok user, Robin, shared her experience buying watermelons at Walmart from her home in Texas. She shows a basket of seemingly normal watermelons, but one of them has completely collapsed as if it had been deflated by a balloon.
The watermelon purchased by Robin Source: TikTok
Robin warns viewers not to buy Walmart's watermelons, claiming that the fruits are not real, and even suspecting their ingredients and origin.
Of course, watermelon will not be fake, this is an anomaly that occurs during the preservation and transportation of watermelon pulp.
First of all, we need to know that the texture of the fruit is caused by the difference in the microstructure within the pulp. During the ripening process, the common changes of hemicellulose and cellulose lead to changes in cell wall structure and the dissolution of pectin between cells, which changes the mechanical properties of pulp tissue, which is the main reason for texture changes.
Differences in fruit appearance, flesh cross-section, and microstructure between different watermelon varieties (P1, P2 and their hybrid variety F1) Source: Literature
If the flesh is harder, it means that the degree of cross-linking of cellulose and hemicellulose in the cell wall is higher, the cell wall is stronger, and the fruit body is harder. If the flesh is softer, they are less cross-linked, the cell walls are softer, and the fruit body is more tender.
The flesh of the watermelon in the video is obviously hard, indicating that the cell wall of the fruit has a high degree of cross-linking. One of the reasons for this is the lack of moisture in the pulp.
North America has been drier in recent months, and under drought conditions, cells lose water and contract, and osmotic pressure increases, stressing the cell wall. If a drought is followed by a sudden large amount of water absorption, the cell wall will rapidly swell and may burst, and this stress can cause the pectin and other polysaccharides in the cell wall to rearrange and form a gelatinous substance, giving the pulp an abnormal texture.
显微镜下的西瓜细胞 图源：microscopic images
In addition, if the water is insufficient, the activity of enzymes associated with cell wall degradation (such as gliase, cellulase, etc.) in watermelon may be inhibited. Changes in enzyme activity affect the softening process of the pulp, resulting in the flesh not softening normally during ripening, but rather the formation of a gelatinous or hard structure.
In addition to the lack of moisture, watermelons undergo drastic temperature changes during preservation and transportation, such as through the cold chain, which may disrupt the normal structure of pulp cells, causing pectin and other polysaccharides in the cell wall to rearrange and form a gelatinous substance. In this case, the flesh will show an increase in hardness opposite to ripeness.
Of course, it is not excluded that these plastic watermelons are stored for too long after ripening, which may also cause gelatinization of the pulp.
Do you think that gelatinization of the pulp is the only phenomenon of poor watermelon preservation?
Also in June of this year, another TikTok user, Gabriela, also bought a fresh-looking watermelon at a supermarket in Seattle. However, when she starts cleaning the watermelon, things get weird. The green watermelon rind began to peel off like a peeled orange under the water, revealing a light green inner layer.
Source: TikTok
Gabriela also suspected that she had bought fake watermelons, feeling that the fruits in the United States were all hopeless. Actually, this is also a truth. If a watermelon is frozen during transportation or storage and then thawed, the skin may fall off due to drastic changes in temperature.
Watermelon with the skin off Source: tiktok
In short, these are broken watermelons......
We do not rule out encountering scientific and technological ruthlessness in reality, but you say that the watermelon you eat is fake, which is too much, after all, the cost of making a decent fake watermelon is much higher than growing a watermelon.