When it comes to spring dishes, toons must be on the list, and among the many spring vegetables, it makes those who love it want it with its unique fragrance.
However, it is listed by many people as a must-eat toon, and it is often criticized for its "nitrite" content.
How did the unique smell of toon come about? How to remove nitrite from toon? "Life Times" interviewed nutrition experts to answer questions and teach you to eat toons scientifically.
Experts interviewed
Fan Zhihong, Professor, College of Food Science and Nutritional Engineering, China Agricultural University
Zhong Kai, Ph.D. in Food Safety and Deputy Director of Kexin Food and Nutrition Information Exchange Center
Is toon fragrant or smelly?
Toon is a vegetable with excellent nutritional value, not only rich in minerals such as potassium, calcium, magnesium, etc., but also the content of B vitamins is among the best in vegetables.
The "Compendium of Materia Medica" records: "Toon leaves bitter and warm, boiled water to wash sores and scabies, young buds (yuè, interpretation: boiled) food, wind and detoxification; White bark and root bark, bitter, warm, non-toxic. ”
It is one of the few woody vegetables and is also known as the "vegetable of the tree".
And people's impression of toons in daily life is as polarized as coriander. Some people find it unique in fragrance, while others find it very pungent and difficult to lower their mouths.
What exactly does toon smell like?
1. Toon contains a large amount of glutamic acid, which is a flavorful amino acid and a natural preservative that comes with food.
2. Toons contain terpenes, sesquiterpenes and other substances, the smell of such substances is like a collection of esters, florals, fruits, sweets, herbs and other flavors, such as caryophyllene contained in toon leaves, there is a "mixed smell of citrus, camphor and cloves".
3. Toons also have sulfur-containing compounds, often showing the special smell of garlic, onions, and leeks, which is also the reason why toons have a pungent odor.
How did the nitrite in toon come about
Toons contain a lot of nitrates, and the nitrite content is much higher than that of ordinary fresh vegetables.
In fact, the nitrates and nitrites in toons are the key to plant metabolism of nitrogen and are inevitable in the plant growth process.
Toon also contains a substance called nitrate reductase, which can turn nitrate into nitrite.
Since this enzyme is mainly found in leaves, the nitrite content in toon leaves is higher than in stems, and the nitrite content of old shoots is generally higher than that of young shoots.
In addition, during the pickling process, nitrate reductase turns nitrate into nitrite acid.
Combining data from multiple studies, toon nitrite levels ranged from a few milligrams per kilogram to 160 milligrams per kilogram.
If you want to poison an adult, you need about 300~500 mg of nitrite, that is, you need to eat at least 2 kg of toon.
Therefore, as long as the way of eating is scientific and appropriate, the possibility of poisoning by eating toons is not great.
6 details to eat toons safely
If you want to taste the umami limited to spring, try the safe way to eat it recommended by nutrition experts.
Choose toon buds with a tender texture
The nitrate content of toon germination is low at the beginning of germination, and as the toon bud continues to grow, the nitrate content also increases.
Toon shoots are usually purplish-red, which is the color of anthocyanins, carotenoids, and various flavonoids. As the shoots mature, the purplish red color gradually disappears.
When buying toon, try to choose purple-red shoots, and do not store them for too long after buying.
Choose fresh toon buds
Toons often have a time difference of two or three days from harvest to food.
After harvesting, a large amount of nitrate will be gradually converted into nitrite during storage at room temperature; If refrigerated in time after harvesting, it will also reduce the conversion rate of nitrite.
The lower the freshness, the greater the risk of nitrite. If the leaves fall off when touched, it indicates a high nitrite content.
Blanching is a critical step
If the toon buds are not fresh enough, but the aroma is still there, it is a pity to throw them away, you may wish to blanch them.
Blanching in boiling water for a while can remove more than 2/3 of nitrite and nitrate, while also better preserving the green color of the toon.
If it is not your own freshly picked toon, whether it is cold mixed, stir-fried or fried toon fish, you may wish to blanch it first, which can greatly improve the safety of eating toon.
Blanch water before preservation
Research data show that blanching for 50 seconds and then freezing, not only the safety is greatly improved, but also vitamin C can be better stored.
When frozen for 2 months, the vitamin C content of blanched toons was equivalent to 71% of fresh products, while only 35% were not scalded.
After blanching, put it in a sealed plastic bag and place it in the quick-freezing compartment of the refrigerator, which can be stored for more than 1 month, maintaining the tender green and aromatic characteristics. But if you freeze it for too long, the color and texture will gradually deteriorate.
Pay attention to the time of pickling
Many people like to salt toons for two or three days before eating, which is a very unsafe habit.
After pickling the toon, the nitrite content will rise rapidly, reaching a peak in three or four days (when the salt content is 10%~20%), and the content far exceeds the license standard.
The safest way to do this is to marinate the blanched toons for 2 weeks and wait for the nitrite content to decrease before eating. Adding vitamin C, ginger, garlic and other ingredients can reduce the amount of nitrite in pickling.
Eat with vitamin C-rich foods
Toon itself has a higher vitamin C content than ordinary vegetables and fruits, and if you can eat fresh toon, vitamin C can help block the formation of carcinogen nitrosamines.
If the toon is not fresh enough but you really want to eat it, you may wish to eat it with other fresh fruits and vegetables to try to avoid the hidden dangers caused by nitrite. ▲
Editor of this issue: Xu Menglian
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