Chemical name NaCl. In the famous painting "Du's Last Supper", Bai Jiata painted an inverted salt pot in front of Judas who betrayed Jesus. The purpose of this painting is to metaphor the evil of Judas. In ancient times, the status of salt was quite high. If the salt pot is knocked over while eating, it will be considered ominous or evil.
It is reasonable for human beings to attach so much importance to salt. Because salt is an essential substance to maintain normal physiological function and health. Sodium ion and chloride ion in salt are important substances to maintain intercellular water balance and blood acid-base balance. Sodium ion can coordinate blood pressure and blood volume, and can also promote the conduction of nerve impulses. In addition, the contraction of the heart and muscles is also inseparable from salt. Experts believe that ordinary people need about 4- 10g of salt every day, of which the daily food itself contains 1-2g, and the rest of the salt should be added during cooking. Patients with nephritis, hepatitis and heart disease should appropriately control their daily salt intake according to the doctor's advice, and patients with hypertension should also appropriately reduce their salt intake. Long-term excessive salt intake is the cause of hypertension, kidney disease and heart disease, and the incidence of arteriosclerosis is also proportional to salt intake.
Salt is not only edible, but also an important industrial raw material, which can be used to make soda ash, caustic soda, hydrochloric acid, polyvinyl chloride and so on. Electrolytic melting of sodium chloride can produce metallic sodium. In agriculture, salt solution is used to select seeds to ensure high germination rate. Sanitation workers in the city spray salt water to melt the snow on the road to ensure the safety of vehicles and pedestrians. In the hospital, you can use salt water instead of disinfectant to clean the wound. In daily life, salting fish can keep it for a long time. Salt is extremely abundant in nature. The vast sea is the hometown of salt. If all the salt in seawater is extracted and spread on the earth's surface, a large "salt blanket" with a thickness of about 40 meters can be formed to cover the earth. At present, the world produces about 654.38 billion tons of sea salt every year. According to this quantity, these salts can be used by human beings for 500 million years.
2. sugar
There are several kinds of sugar, such as brown sugar, white sugar and rock sugar. Brown sugar is a mixture of sucrose and molasses, and white sugar is made from brown sugar through washing, centrifugation, honey separation and peeling. Rock sugar is formed by recrystallization of white sugar under certain conditions. Their chemical composition is sucrose. In long-term storage of brown sugar, molasses will be oxidized, which will make the color dark and sour, so brown sugar can no longer be eaten.
The function of sugar in the body is only to supplement energy, or to store it in the body as glycogen, which has simple function and basically contains no other nutrients. Many studies at home and abroad show that too much sugar or improper diet often leads to myopia, dental caries, diabetes, obesity, fractures and other diseases. In fact, without sugar, the human body is not short of sugar, because the rice, noodles, fruits and vegetables we eat every day all contain sugar. According to the regulations of nutrition experts, children's sugar intake per kilogram of body weight should not exceed 0.5 grams of white sugar per day, while adults' sugar intake per kilogram of body weight should not exceed 0.55 grams of white sugar. To this end, the World Health Organization proposes: Please eat less sugar for your health.
3, monosodium glutamate
1908 One day, Japanese chemist Ikeda found kelp and cucumber soup particularly delicious when drinking it. This aroused his professional sensitivity, but he made a chemical analysis of kelp and got a very chemical substance-sodium glutamate. The business-minded Japanese quickly turned this invention into a commodity and named it "essence", thus MSG quickly became popular all over the world.
Some people think that eating too much monosodium glutamate will lead to poisoning, which has no scientific basis. On the contrary, the delicious taste of monosodium glutamate can stimulate taste cells and excite digestive glands, increase appetite and promote digestion. Monosodium glutamate also has certain medicinal value, which can change the nutritional status of human body and increase acetylcholine in brain, thus treating neurasthenia; Regular and moderate consumption of monosodium glutamate can improve children's developmental retardation; Glutamine formed by the combination of sodium glutamate and ammonia in blood has a good effect on treating hepatic coma and epilepsy caused by elevated blood ammonia. However, when using monosodium glutamate, we should pay special attention to the temperature. If it is heated above 120℃ during cooking, sodium glutamate will undergo chemical changes and become sodium pyroglutamate, which will not only reduce the umami taste but also be slightly toxic. Therefore, when cooking and cooking soup, monosodium glutamate should be added when leaving the pot.
The dosage of monosodium glutamate should be appropriate, generally not more than five thousandths. If you put too much monosodium glutamate, people will feel thirsty and sour after eating it. Because monosodium glutamate is alkaline, it should not be mixed with acidic dishes such as vinegar to avoid acid-base neutralization. In addition, babies should eat less monosodium glutamate, because monosodium glutamate will form complex zinc glutamate with zinc in the human body, and then dissolve in water and excrete it, resulting in zinc deficiency in babies and affecting children's development.