Watermelons wrapped in plastic wrap have too many bacteria, which can cause poisoning? Remember these 4 points to eat watermelons safely!

Author: Zhang Yu, researcher at the Chinese Center for Disease Control and Prevention, supervisor of medical doctorate and master's degree students

Reviewer: Zhong Kai, Director of Kexin Food and Health Information Exchange Center

"It is found in many places in Huaixiang, and is a natural jade ball. When broken, it is crystal clear, and when chewed, it cools the teeth. It can clear away the heat of the enemy, and it can make people drink more freely. There is no such thing at Dongmen, and it is like a cluster of snowflakes on an ice plate." This poem from the Song Dynasty, titled "Watermelon", takes us to appreciate the refreshing sweetness of watermelon in the hot summer, which is a refreshing taste. Compared with other fruits, watermelon is not only moderately sweet, but also rich in water, vitamins and minerals, so it is loved by men, women, young and old. In recent years, there are more and more "health tips" about watermelon on the Internet, and each one seems very considerate, but in fact, most of them are rumors.

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01

Rumor: Seedless watermelons are said to be caused by birth control pills and should not be eaten

Analysis: Fake!

Seedless watermelon is a kind of watermelon without seeds in the flesh. Its full name is triploid seedless watermelon. It is bred by hybridizing ordinary watermelons using the method of artificially induced polyploidy and has nothing to do with contraceptives.

It is normal to spit out the seeds when eating watermelon, but many people find this troublesome, which provides a market for the cultivation of seedless watermelons.

Ordinary watermelons are diploid, with 2 groups of 22 chromosomes in total. They can form gametes through meiosis, and then achieve pollination and fruiting. In this process, seeds (i.e. watermelon seeds) can be formed. During the seedling stage of diploid watermelons, if they are treated with colchicine, the number of chromosomes in the watermelon will double and become tetraploid. Then, by hybridizing the diploid watermelon with the tetraploid watermelon, a triploid watermelon is obtained. The so-called triploid contains three sets of chromosomes, and it is impossible to undergo meiosis to form gametes, and there is no way to produce seeds through pollination.

As for why there are watermelons without seeds, the reason is very simple. Watermelons are gourds, which are fruits unique to the Cucurbitaceae family. The flesh we usually eat is developed from the receptacle, which has no direct relationship with whether there are seeds.

02

Rumor: It is said online that overnight watermelon cannot be eaten, it will cause poisoning

Analysis: Fake!

Whether a watermelon can be eaten after it is cut depends on whether it has gone bad, as well as the type and number of pathogenic bacteria, and has no direct correlation with whether it has been left overnight. The phenomenon of poisoning after eating watermelon does exist, mainly due to the serious corruption and deterioration of watermelon under the action of bacteria, and the presence of certain pathogenic bacteria, such as Salmonella, Staphylococcus, Escherichia coli, etc.

Under normal circumstances, the inside of a fresh watermelon that has not been cut is basically sterile. Once the watermelon is cut, the cut surface will be contaminated by bacteria. The number and type of bacteria mainly depend on the storage environment, temperature and time. Generally speaking, the more bacteria there are in the environment, the higher the temperature and the longer the time, the more number and type of bacteria will grow in the watermelon.

However, if you clean the knife and cutting board before cutting the watermelon, and wrap the watermelon that cannot be eaten immediately after cutting with plastic wrap and store it in the refrigerator, the total amount of bacteria will be greatly reduced even after overnight. In the absence of pathogenic bacteria, the safety of eating can be guaranteed. On the contrary, if the watermelon is left at room temperature after cutting, or the knife and storage environment are not clean, there may be a risk of diarrhea or poisoning even if it is left for several hours during the day before eating.

Therefore, the key issue is not whether to store the watermelon overnight, but the storage method after cutting it. However, it is still recommended to eat the cut watermelon as soon as possible. If the color and smell have changed significantly, it is better not to eat it for safety reasons.

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03

Rumor: Watermelon is too sweet because it is sweetened with sweeteners

Analysis: Fake!

The fact that watermelons are becoming sweeter is actually the result of the combined effects of breeding and cultivation techniques.

Sweetness is a taste. The sugar content of the fruit and the type of sugar will affect the sweetness. The sugar content of watermelon is generally around 5%-12%, and can be as high as 15%. Watermelon contains a variety of sugars such as fructose, sucrose and glucose, among which fructose has the highest sweetness.

During the development and ripening process of watermelon fruit, the sugar and organic acid content determines the taste of watermelon. Wild watermelon is not sweet, but bitter and sour. Through continuous hybridization and breeding, the sweeter varieties are retained to improve the taste of watermelon. In addition, scientific cultivation technology also has a great influence on the taste of watermelon. Studies have found that a large temperature difference between day and night, moderate soil moisture during the ripening period, and timely harvesting will increase the sweetness of watermelon.

The rumor on the Internet that watermelons are injected with sweeteners is not reliable. The injection process will leave pinholes on the surface of the watermelon, which will become channels for bacteria and mold to invade, and the fruit will easily deteriorate. Injecting sweeteners cannot guarantee that they are evenly distributed in the fruit, and will also cause local scars that affect the taste, which is not worth the loss.

However, in the agricultural production process, some fruit and vegetable quality improvement technologies are indeed used to increase yield and sugar content, such as spraying some surface fertilizer on the leaves of watermelon plants, but this does not affect the edible safety of watermelon.

04

Rumor: Pregnant women and diabetics cannot eat watermelon

Analysis: Fake!

The glycemic index (GI) of watermelon is high, but the sugar content is not high, so you can just control the total amount.

Every food has its own unique nutritional value and flavor. There is no absolute prohibition on eating. It is a question of how to choose and how much to eat. For pregnant women and diabetics, excessive sugar intake will affect blood sugar load. Therefore, it is necessary to consider the glycemic index (GI) and sugar content.

GI refers to the degree of blood sugar fluctuation after 100 grams of food is digested and absorbed. The higher it is, the faster the blood sugar rises, and the lower it is, the slower the blood sugar rises. The GI of watermelon is 72, which is indeed very high. More than 90% of the weight of watermelon comes from water, and the sugar content per 100 grams is only 5.5 grams, which is much lower than other fruits of the same weight. Calculating the GI and sugar content of food together can obtain the glycemic load (GL), that is, the ultimate impact of food on blood sugar. The GL of watermelon is 3.96, which is at a relatively low level. In other words, as long as the total amount of watermelon eaten is controlled, there is no problem for pregnant women and diabetics to eat watermelon.

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in conclusion

Finally, here are some health tips for eating watermelon. First, the cut watermelon must be eaten as soon as possible and should not be stored for too long. Second, although watermelon is good, it should not be consumed too much, especially for those with poor blood sugar control and weak digestive systems. Third, watermelon should not be eaten as a main meal or midnight snack. Fourth, people with oral ulcers are advised to eat less watermelon.

References:

1. Cao Hong, Jin Rongrong, Yuan Jinxin. Research and development of seedless watermelon[J]. Journal of Anhui Agricultural Sciences, 2015, 43(29): 68-69.

2. Li Jian. Scientific interpretation of whether overnight watermelon is really poisonous [J]. China Food, 2022, (12): 141.

3. Dai Xiaopei. Scientific interpretation of the sweetness and sugar content of fruits[J]. Chinese Food, 2020, (19): 134-135.

4. Chen Fuquan, Chen Qi, Huang Shuizhao. Preliminary report on improving sugar content and yield of watermelon by fruit and vegetable quality improvers [J]. Chinese Vegetables, 2005, (3): 24.

5. Wei Libo. How can diabetic patients eat watermelon safely? [J]. Family Science·New Health, 2017, (6): 58.

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