"Pot simmering soup" is a kind of flavor dish popular in southern China. It uses a special large crock, the bottom of which can be burned, and the crock is built with an iron frame. The chef puts the small crock filled with soup layer by layer into the iron frame in the crock, then lights charcoal, and uses the high temperature generated by charcoal fire to cook the soup in the crock. The big crock for making "crock simmer soup" is about 13 meters high and is made of coarse pottery. There is a circular iron cylinder at the bottom of the cylinder, which can hold charcoal for burning fire. There are three layers of iron frames in the cylinder, which can hold about 30 small cylinders. The top of the cylinder has an iron cover, which can be opened at any time. Charcoal and crock are put in from the top with iron clips. The small crock for soup is about18cm high and 20cm in diameter. It has a small handle, which can be held by hand and served on the table. In addition, there is a small lid with a small hole on it, which is used to discharge excess heat when simmering soup. When simmering soup, it is necessary to clean all kinds of raw materials, put them in a small crock, then add spices, add clean water, preferably purified water, cover them, stack the crock on the iron frame in the crock, light charcoal, simmer for 8- 12 hours and take out the soup. There are many kinds of materials for making "crock simmer soup", including chicken, duck, beef, pork, seafood, game, bamboo shoots, fungi, bean products and vegetables. When making "clay pot simmer soup", we should also pay attention to the following points: 1 Generally, only clear water or purified water is mixed in the clay pot, and fresh soup can not be used, so as to ensure the original flavor of simmer soup with different flavors. 2 Before the crock is capped, the mouth of the crock should be sealed with a piece of aluminum foil paper, and then capped to ensure that the crock is well sealed. The simmering time should be determined according to the different properties of different raw materials. Generally, raw materials are stewed for 8 hours, while raw materials with relatively old and tough texture, such as beef, native chicken and old duck, need to be stewed for 10 ~ 12 hours. The firepower of different positions in the big tile cylinder is different, so we should pay attention to the reasonable collocation of large and small fires when simmering. Generally, the soup in a crock is cooked with high fire first, and then boiled with low fire. After a pot of soup has been stewed for about 4-5 hours, it is necessary to "turn over", that is, change the position of the crock to avoid the crock being stewed dry because it is close to the position with high firepower. Note: eight essentials of soup ● Choosing the right ingredients is the key to making fresh soup. The raw materials used to make soup are generally animal raw materials, such as chicken, duck, poultry bone, lean pork, pork elbow, pork bone, ham, dried salted duck, fish and so on. , but it must be full of flavor, small smell and less blood stains. This kind of food is rich in protein, succinic acid, amino acids and nucleotides. Water-soluble nitrogen-containing extracts from poultry meat, including creatinine, protein, creatine, creatinine, urea, amino acids and other non-protein nitrogen-containing substances, are the main sources of soup flavor. ● Fresh food is not the "fresh" that has always been emphasized. Modern freshness refers to 3-5 hours after the slaughter of fish and livestock. At this time, various enzymes in fish or poultry meat decompose protein and fat into amino acids, fatty acids and other substances easily absorbed by human body. This time is not only the most nutritious, but also the best taste. ● Cooking utensils should choose fresh soup and simmer in an old crock, with the best effect. A crock is clay made of raw materials that are not easy to transfer heat, such as seasonable, feldspar and clay, and fired at high temperature. It has good air permeability and adsorption, and also has the characteristics of uniform heat transfer and slow heat dissipation. When simmering fresh soup, the crock can transfer the external heat energy to the internal raw materials in a balanced and lasting way. A relatively balanced ambient temperature is conducive to the mutual penetration of water molecules and food. The longer this mutual infiltration lasts, the more delicious ingredients spill out, the fresher the taste of the soup and the crisper the texture of the stew. ● The key to proper simmering soup is: the fire is boiled and the fire is simmered slowly. In this way, fresh and fragrant substances such as protein extract in food can be dissolved as much as possible to achieve the purpose of fresh, mellow and delicious taste. Only slow fire can make the extract dissolve more, clear and strong. ● Water distribution should be reasonable. Water is not only a solvent for delicious food, but also a medium for food heat transfer. The change and dosage of water temperature have a direct impact on the flavor of soup. The water consumption is generally three times the weight of the main course of the stew, and the food should be heated together with cold water, that is, don't simmer the soup directly with boiling water, and don't add cold water halfway, so that the nutrients of the food will overflow slowly, and finally the soup will be clear. ● Matching should be suitable for the fixed matching mode between many foods, so that the nutrition is complementary, that is, the "golden matching" on the table. For example, kelp stew, acidic food meat and alkaline food kelp have a "combined effect", which is the "longevity food" of Changshou area (Okinawa area). In order to make the soup more pure, a variety of animal foods are generally not stewed together. ● Pay close attention to the order in which seasoning materials are put into operation. In particular, don't put salt in the soup first. Because salt has a penetrating effect, it will drain the moisture of raw materials, and the protein will solidify, and the umami flavor is insufficient. Generally speaking, the temperature of 60℃ ~ 80℃ is easy to cause some vitamins to be destroyed, while cooking soup keeps the food temperature at 85℃ ~ 100℃ for a long time. Therefore, if vegetables are added to the soup, it is necessary to match them as you eat, so as to reduce the damage of vitamin C. Add seasonings such as monosodium glutamate, sesame oil, pepper, ginger, onion, garlic, etc. to make the soup unique, but be careful not to use too much, so as not to affect the original flavor of the soup. ● When drinking soup, pay attention to the saying that "drinking soup before meals makes you slim and healthy" and "drinking soup after meals makes you fatter", which has certain scientific reasons. Drinking soup before eating is equivalent to adding some "lubricants" to the upper digestive tract to make the food swallow smoothly. Drinking soup from time to time during meals is conducive to the dilution and stirring of food, and is conducive to the absorption and digestion of food in the gastrointestinal tract. At the same time, drinking soup before eating can partially fill the stomach, which can reduce the inclusion of staple food and avoid excessive calorie intake. And eating soup after meals can easily lead to overnutrition and obesity. It is worth noting that we should not unilaterally think that the "refined soup" made of fish, chicken and other raw materials is the most nutritious. Experiments show that no matter how long it is cooked, there are still nutrients left in the "meat residue". It is unscientific to drink only soup and not eat "meat residue". Usually, the best cooking time of fish soup is about 1 hour, because the nutrients in the soup mainly come from amino acids. If the heating time is too long, new substances will be produced, but the nutrients will be destroyed. Chicken soup and sparerib soup generally take about 1~2 hours. After this time, high purine will appear in the soup. Purine in soup can cause uric acid to deposit in the blood. Drinking soup with high purine will make people fat, and may also cause diabetes, gout and cardiovascular and cerebrovascular diseases. Vegetable and fruit soup is usually boiled in water, which can avoid the damage of nutrients caused by long-term heating, mainly to reduce the damage of vitamins C and B. Don't cover the water with vegetables, keep it isolated from the air and reduce the loss of nutrients. If it's old fire soup in Guangdong, it usually takes more than 2 hours to cook, and if it's stewed, it takes more than 4 hours. Cook for twenty or thirty minutes with strong fire, and then simmer slowly. The soup cooked in this way is steaming, original and delicious. As for heat, the temperature of 60℃ ~ 80℃ will destroy some vitamins, and the food temperature should be kept at 85℃ ~ 100℃ for a long time when cooking soup. Therefore, the key to simmering soup is "big fire to cook, small fire to stew slowly". The temperature of cooking noodles shall be based on the boiling degree of noodle soup. Don't use fire to boil the soup, lest the protein molecules in the soup move violently and make the soup turbid. Other soups are boiled with strong fire, and then with medium fire or small fire according to the cooking degree of the ingredients. Only in this way can the fresh and fragrant substances in food be dissolved to the maximum extent, so that the soup is clear and mellow, and the original nutrients can be locked to the maximum extent.