Chemical Engineering in Daily Life – Question 16: Why is it necessary to blanch and remove impurities from wild vegetables before eating them? - Standard answer already available
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This post was last edited by yjqin1 on 2015-8-22 at 22:12. Our Chinese nation has survived to this day after going through countless hardships. Among these, apart from foreign invasions, the main threat comes from droughts, with no food or water available. This is also why one of my main areas of research is seawater desalination and the utilization of brackish water, and the other is sugar production from straw. Today, China’s desalination plants ensure that each person has 1 liter of water to drink per day. Coupled with well-developed highways and high-speed railways, the Chinese people will not die of hunger or thirst. In the past, even without droughts, the spring famine would set in right after the Spring Festival. Enduring the spring famine meant going hungry and eating chaff and weeds. Eating wild vegetables is what is meant by \"eating throat vegetables\". It was not the five grains that enabled the Chinese nation to thrive to this day, but wild vegetables. The wild vegetables eaten at that time in spring mainly included shepherd’s purse, chickweed, goosefoot, cocklebur, sow thistle, wild amaranth, wood sorrel, dandelion, sour plantain, water spinach (sheepskin leaf), St. John’s wort (scientific name: Potentilla discolor), the rhizomes of certain plants, woodruff, willow buds, and poplar buds. Many wild vegetables are poisonous. The traditional method among ordinary people is to first blanch it (cook it in boiling water), then soak it in cold water, and afterwards use it in various ways. What is the chemical principle behind blanching first and then removing it?
Blanching is to enhance the destruction of toxins through heating, while soaking involves cleaning, dissolving, and penetration.
I agree with you; boiling water has the effect of destroying proteins
By heating it to a high temperature, the toxic substances contained in the material break down; most of these breakdown products are non-toxic, which is why it is common to blanch vegetables. As for soaking in cold water, the purpose is to lower its temperature to a level safe for human consumption, thereby preventing burns caused by high temperatures.
Blanching is used for disinfection; the toxic substances in vegetables are generally broken down into non-toxic substances in the wastewater. Using cold water for rinsing serves to prevent high temperatures from destroying nutrients such as vitamin C, and it also helps improve the taste. Chinese people place quite a lot of emphasis on taste
There are many different situations. First, blanch to break down the cell walls and membranes. Protein-based toxins can be inactivated through irreversible denaturation (it is uncertain whether denatured toxins remain toxic). For alkaloids, it’s best to blanch them in some vinegar. It can increase the solubility in water and reduce toxicity.
For thousands of years, the Chinese nation has survived in difficult times by eating wild vegetables, and they have extensive experience in this regard – an experience gained at a great cost. They do not eat just any wild plant they come across. Eating wild vegetables only occurred in the extremely special situation of the Red Army crossing the grasslands. The Red Army soldiers from the south were hungry, but they did not recognize the plants found in the mountainous areas, and many of them lost their lives as a result. In fact, apart from amaranth, the common wild vegetables are not highly toxic; the main harmful components in them are nitrates and oxalates. I hope readers will provide answers accordingly.
This post was last edited by yjqin1 on 2015-8-22 at 22:12. Standard answer: When blanched in boiling water, the cells break apart, allowing oxalates and nitrates to be released; of course, proteins and other substances are also inactivated by the heat. Soaking in cold water is equivalent to an extraction process, using water to dissolve these oxalates and nitrates. Spinach also contains a lot of oxalates; I usually drink clear soup with plenty of water. Drink half and throw away the other half. The principle is the same. Furthermore, wild amaranth (also known as \"renqing cai\" or \"renxing cai\") contains a very high concentration of nitrates, which can cause diarrhea in pigs if they consume too much of it. The problem with nitrates is that they can be reduced to nitrites. Wild amaranth is different from the native amaranth in our country (red amaranth); it is an invasive species that was introduced from the United States during the Guangxu period. When I was young, I raised three pigs in total. The wild vegetables that pigs prefer most for feeding are shepherd’s purse, purslane, amaranth (blood sorrow), and wild amaranth. Rabbits like to eat plantain, bitterweed, and grass.