​Recently popular! Some netizens got "poisoned" after eating it... Southerners should pay special attention

Recently, it is the season for cassava to be put on the market. On a certain social platform, "cassava sweet soup" has become a high-frequency word. Many netizens posted photos of their homemade cassava sweet soup and commented: "It is so delicious, one mouthful after another is very addictive" and "It is chewy on the outside and soft and fluffy in the middle, very magical"...

The picture comes from the Internet

But some netizens suspected poisoning after eating it:

The picture comes from the Internet

What's going on?

Cassava is really poisonous

Cassava is divided into three types: edible, feed and industrial cassava. Among them, only edible cassava is edible for human consumption. But don't worry, the cassava we can buy on the market is generally edible cassava.

So, is it safe to eat cassava? Not really.

Let me first state the conclusion: raw/fresh cassava is indeed toxic. The toxicity comes from two cyanogenic glycoside compounds in raw cassava, one called linamarin (accounting for about 95%) and the other called radix rutin[1]. These two substances, when hydrolyzed by the linamarinase contained in cassava itself, will produce toxic hydrocyanic acid. If you are a Level 10 contestant of "The Legend of Zhen Huan", you must remember the famous "cassava powder incident". The bitter almonds that An Lingrong used to commit suicide also contained hydrocyanic acid as a toxin.

Some data show that eating 150g to 300g of unprocessed raw cassava may cause poisoning.

The reason why cassava is divided into three types: edible, feed and industrial cassava, is also based on the content of cyanogenic glycosides. According to the standards of the Codex Alimentarius Commission (CAC), when cassava is peeled, soaked and processed, if the content of cyanogenic glycosides is below 50 mg/kg, it can be classified as edible cassava.

It's not surprising that cassava is poisonous. After all, cassava comes from the Euphorbiaceae family, which is a "terrible" family. Euphorbiaceae plants are generally poisonous. In addition to cassava, another delicious and poisonous food is taro (you can review the previous article "Reasons to persuade you to eat more taro, one is enough!"), which must be carefully peeled, soaked and thoroughly cooked before eating.

In addition to the above methods, fermentation, baking, sun drying, crushing and other methods can also remove hydrocyanic acid from cassava tubers [1].

Cassava slices. Copyright image. Reproduction may cause copyright disputes.

If it is dangerous, why is cassava still used as a staple food?

Although cassava is poisonous when eaten raw, one fact that cannot be ignored is that the starch content of cassava is as high as 70% to 80%.

It has a soft and sticky texture and a large yield, but it has low requirements for the growing environment and cultivation level. It is drought-resistant and resistant to barrenness. To put it bluntly, eating cassava is low-cost and can resist hunger. These characteristics make cassava widely planted in areas with backward agricultural levels (mainly in Africa) and become the staple food for local people to survive. Now, cassava is the third largest source of starch in the world, ranking closely after rice and corn. According to statistics, cassava is the main food for 800 million people.

However, since cassava is mostly starch and its nutrients are very simple, eating large amounts of cassava for a long time can easily lead to a lack of high-quality protein, vitamins and other nutrients.

Comparison of some nutritional components of cassava, rice and steamed bread

Data from: Chinese Food Composition Table (Sixth Edition)

Cassava has a low protein content, but its potassium, vitamin C and vitamin B1 contents are higher than rice and steamed bread, which is related to the fact that cassava is less processed than rice and steamed bread, which are made from rice and wheat. For example, after cassava is processed into cassava flour, the protein content is only 0.08g/100g, and the vitamin C and vitamin B1 contents are 2.96mg/100g and 0.007mg/100g respectively.

Because the detoxification process is troublesome and the nutritional value is not very high, people in agriculturally developed areas generally do not choose cassava as a staple food. However, as long as it is delicious, Chinese people have never been afraid of something that is a little toxic, such as pufferfish and various Yunnan mushrooms, which are not a big obstacle for foodies, let alone cassava, which is just "tummy trouble".

Various types of "sugar water" made from cassava are very popular in many areas in the south. Taro balls, mochi, and "pearls" in milk tea made from cassava starch are also very popular.

Cassava syrup. Copyrighted images from the gallery. Reproduction may lead to copyright disputes.

How to enjoy delicious food safely?

To enjoy cassava food in a healthy, safe and fast way, it is recommended that you pay attention to the following points:

1. Choose the right variety

Chinese agricultural scientists have developed low-toxic cassava varieties, such as "Huanan No. 9", "Guire No. 10" and "Gui Cassava No. 11".

However, even if it is a low-toxic variety, you should not consume it in large quantities at one time. In addition to the toxicity issue, you should also consider the calorie issue caused by eating a large amount of starchy food.

2. Peel and soak, cook thoroughly, and don’t eat too much at one time

The content of cyanogenic glycoside compounds in cassava peel is very high. By peeling and soaking in clean water for a long time (some say it should be soaked for 1 week, changing the water every day), the content of cyanogenic glycoside compounds can be reduced and the toxicity can be reduced.

It should also be cooked thoroughly during production. High temperature heating can inactivate enzymes that can convert cyanogenic glycosides, making it impossible for them to convert cyanogenic glycosides into toxic hydrocyanic acid. Therefore, thorough cooking is an important method for detoxifying cassava. It is important to open the lid when cooking cassava to allow the converted hydrocyanic acid to evaporate.

It is also important to note that you should not eat too much at one time. It has been reported that some people may have enzymes in their intestines that can convert cyanogenic compounds into hydrocyanic acid, so some people may experience mild poisoning symptoms such as vomiting even if they eat cooked cassava.

3. Buy cassava flour directly

This method can better ensure non-toxicity and is easier to process into delicious food.

Finally, I would like to recommend a simple and easy-to-make winter cassava delicacy to everyone~

Taro Balls and Egg Custard

raw material:

Cassava flour, sweet potato puree, sugar, eggs, wolfberry, dried osmanthus

step:

1. Mix tapioca flour and sweet potato puree in a ratio of 2:1, add appropriate amount of white sugar and mix well. You can add appropriate amount of water or milk to knead into a non-sticky dough. Roll the dough into thin strips and cut into small pieces of appropriate size, slightly shape and roll into round shapes. Add water to a pot and bring to a boil, add taro balls, cook until done, remove from the pot and rinse with cold water for later use.

2. Pour clean water back into the pot and bring it to a boil. Beat the frangipani. After it is cooked, add the taro balls and wolfberries and cook for 1 to 2 minutes. You can add sugar according to your personal taste. Sprinkle with dried osmanthus flowers after serving and you can enjoy it.

This taro ball custard is made with eggs to make up for the lack of high-quality protein in cassava and sweet potatoes. If you have time, you can also cook red beans in a pressure cooker in advance and add them to the taro ball custard to further increase the content of minerals and dietary fiber, and also make this dessert taste richer.

References

[1] Zhang Zhenwen, Li Kaimian. 100 Questions on Cassava and Its Processing and Utilization[M]. China Agriculture Press, 2017.

This article is a work of Science Popularization China-Starry Sky Project

Produced by: Science Popularization Department of China Association for Science and Technology

Producer｜China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.

Author: Wang Lu, registered dietitian

Review | Ruan Guangfeng, Deputy Director of Kexin Food and Health Information Exchange Center