The "old fire soup" method, usually cold water, ingredients, boiling and then boiled for several hours. Traditionally, the longer the boiling time, the better the flavor of the soup. In fact, it is not. First, let's look at the effect of soup temperature on food. Animal food in the taste of the material that is low molecular nitrogenous compounds (such as creatine, creatinine, purine base and a small number of amino acids) at lower temperatures that is, protein has not been denatured before the soup can be dissolved in these nitrogen leachate can make the soup taste delicious, and can stimulate the human appetite, so drink the right amount of soup before meals should be a good habit. As for the water-soluble vitamins in food (B and C) and a small amount of inorganic salts (sodium, potassium, etc.), in the process of making soup can be dissolved in the soup, but the amount is not much. Finally, let's look at the dregs of the soup. A pot of soup water solids accounted for about 2% to 5% of the soup, is used in the soup material food in a very small part of the soup; soup raw materials in the protein coagulation and denaturation in case of heat, denaturation of proteins do not dissolve in water and retained in the cooked dregs of the soup. According to the above analysis, we can easily see that drinking soup without eating meat (dregs of soup), is completely unable to get the nutrition of protein, is a kind of wrong eating habits.
In addition, cooking food for a long time, food vitamins, especially water-soluble vitamins (vitamin B and vitamin C) will be destroyed, which is the "old fire soup" is another unscientific aspect
.