Keywords: eating habits, chemical health of food
With the improvement of science and technology and people's living standards, life expectancy and people's happiness index have increased significantly, and people pay more and more attention to scientific diet. In recent years, there have been reports about sudden food safety problems in China, and the harm caused by Sudan red and melamine has made people pay more attention to food safety. However, people have neglected some food safety problems that are frequently contacted in daily life. Although these foods have little impact on human health in the short term, long-term consumption or large consumption will lead to chronic and potential harm. For food consumers, knowing more about food hazards and prevention knowledge and developing good eating habits can prevent the occurrence of food-borne diseases to some extent. In this paper, we will take barbecue, pickled food and overnight food as examples to analyze the chemical causes of harmful substances and the toxicological mechanism of health problems, and put forward reasonable dietary suggestions.
I. Chemical and Toxicological Problems of Barbecue, Pickling and Overnight Food
1, barbecue food
Different nationalities, countries and regions have different eating habits. For example, some people like to eat fried and grilled foods. Roasted mutton, steak, chicken wings and fried fish are common dishes on the table. This kind of eating habit has an increasing trend in our country. Why do people like to eat barbecue food? 19 12 French chemist L.C.Maillard proposed that the non-enzymatic browning reaction, Maillard reaction, occurred between carbonyl compounds and amino compounds through condensation and polymerization. It is found that this kind of reaction not only affects the color of food, but also plays an important role in its flavor. In the cooking process of frying, roasting, baking, frying and so on, the amino acids, peptides, protein and reduced sugars in animal or plant foods have Maillard reaction at high temperature, forming the unique attractive fragrance of pork, beef, chicken, fish and chips that people like.
It was found that compounds harmful to human health, such as heterocyclic amines, acrylamide and polycyclic aromatic hydrocarbons, were produced during food roasting. 1976 A variety of heterocyclic amines were found in grilled sardines, and nearly 30 heterocyclic amines have been identified so far. Acrylamide was found in baked French fries in 2002. Generally speaking, heterocyclic amines from food are mainly low-molecular-weight organic amine compounds formed by pyrolysis of protein components in the cooking process of meat products such as frying, roasting, baking and frying, etc. when the temperature is above 200℃. The formation of heterocyclic amines is related to cooking temperature, cooking time, heating mode and moisture. Studies have shown that when food is cooked at a temperature below 160℃, the formation of heterocyclic amines is very small, but with the increase of temperature, the content of heterocyclic amines gradually increases, for example, when ground beef is fried at 250℃, the content of heterocyclic amines is 6 to 7 times that at 200℃. At the cooking temperature above 200℃, the longer the food is heated, the more heterocyclic amines are formed. The heating mode of burning, roasting, frying and frying produces more heterocyclic amines than the heating mode of stewing, stewing and boiling. This phenomenon may be related to the inhibition of water on the formation of heterocyclic amines. On the other hand, plant foods rich in starch react with carbohydrates at high temperature to produce acrylamide.
The harm of heterocyclic amines and acrylamide to human health has attracted people's attention. Toxicological study found that heterocyclic amines extracted from the carbonized surface layer of roast meat could make the histidine auxotrophic Salmonella typhimurium strain mutate (Ames test), which indicated that the heterocyclic amines produced during food cooking were mutagenic. It is also found that heterocyclic amines can be metabolized by cytochrome P450 and N- acetyltransferase 2 in animals. After N- hydroxylation, heterocyclic amines are positively charged, which is easy to form DNA adducts, causing DNA damage and genetic toxicity. Long-term intake of heterocyclic amines is harmful to human health and may even cause cancer. Animal experiments have found that heterocyclic amines in barbecue and other foods are mutagenic and carcinogenic, which can induce tumors in experimental animals. Acrylamide can be metabolized into epoxypropylamide in animals and humans, and it can cause gene mutation and chromosome abnormality in mammalian somatic cells and germ cells. These chemical and toxicological mechanisms reveal the harmful foreign substances that may be produced in the process of food processing and cooking, and these compounds have mutagenic and carcinogenic effects.
2. Pickled food
Human beings have been processing, making and eating sausages for 1500 years, and traditional foods such as sausage, sausage, ham and luncheon meat are favored by people. Nitrate and nitrite are commonly used as preservatives in the curing process of this kind of meat products, which can prolong the shelf life of food, form the red color and flavor of cured meat and stimulate appetite. However, nitrosamines formed by nitroso and amino groups in meat are a strong carcinogen and teratogenic substance. At present, among 100 nitrosamine compounds that have been detected, ethyl nitrosamine, diethyl nitrosamine and dimethyl nitrosamine have carcinogenic activity to at least 20 animals. Adding a certain dose of dimethylnitrosamine to the feed of rats for 26~40 weeks can induce liver cancer in rats. Therefore, countries all over the world have set strict restrictions on the amount and content of nitrite in meat products to ensure food safety.
The history of pickled folk vegetables in China is more than 3000 years, and later its production technology spread to Japan, South Korea and other countries. Fermented vegetables can keep the nutrition, color and fragrance of vegetables, and are easy to operate, low in cost and convenient to eat, so they are deeply loved by people. However, the problem of nitrosamines formation during vegetable curing is often ignored. How are nitrosamines formed? There are a lot of nitrates in fresh vegetables, and the curing process needs microbial fermentation. Under the action of some bacteria, excessive nitrates in food will become nitrite. Nitrite reacts with amines in food to produce nitrosamines and cause cancer, most of which are esophageal cancer and gastric cancer. The peak time of nitrite production in pickled vegetables is 10-20 days, and vegetables can be produced as soon as 1 day, so it is not suitable to eat pickled vegetables or pickles that are not pickled thoroughly. However, the nitrate in vegetables preserved for more than one month can be destroyed and its harm is reduced.
3. Overnight food
Eating overnight meals is common in China. Many families often prepare rich dishes during holidays or entertain relatives and friends, but leave a lot of meals after meals; Some people will pack some food to eat at home when they have dinner in a restaurant; There are also office workers who make lunches the first day and bring them to work for lunch the next day. In fact, eating overnight meals often is harmful to people's health, and this problem has not attracted enough attention. On the one hand, the harm of overnight food reflects the loss of nutrients and the formation of harmful substances. Vegetables cooked with oil and salt will not only lose nutrients, but also produce nitrite, which will react with amines under the action of gastric acid and nitrate reducing bacteria to produce nitrosamines, which has become a major health hazard. Protein degradation products produced by seafood such as crabs, fish and shrimps overnight will damage the liver and kidney function. On the other hand, the leftover food is exposed to the air, and under the action of bacteria, substances harmful to human body, such as hydrogen sulfide, amine, phenol, etc., are produced, which can induce gastroenteritis or food poisoning. The formation of these harmful chemicals is related to the storage temperature, storage time, food types and eating methods of meals. The amount of nitrite in meals increases with the increase of temperature and storage time. Low temperature can reduce the content of nitrite ingested from overnight meals, but two misunderstandings should also be avoided. One is that it is safe to put meals in the refrigerator, and the other is that it is cold in winter and leftover meals do not need to be put in the refrigerator. In fact, the content of nitrite will increase even if it is kept in the refrigerator for a long time. Leftovers should be kept for 5-6 hours without meals, with breakfast at noon and lunch at night. It is worth mentioning that different kinds of vegetables produce different amounts of nitrite under the same storage conditions. Usually, stem and leaf vegetables are the highest, melon vegetables are slightly lower, and roots and cauliflowers are in the middle. In addition, overnight dishes have been stored for a period of time because of the pollution during eating, and the microbial content in the dishes is high. Therefore, it is necessary to thoroughly heat and thoroughly heat the leftovers before eating to prevent bacteria from entering the human body.
Two, barbecue, pickled and overnight food healthy eating suggestions
Food is the most important thing for the people, and safety is the first thing to eat. Taking some common bad eating habits in daily life as examples, this paper analyzes the chemical causes and toxicological mechanisms of harmful substances, and puts forward the following reasonable suggestions for people's healthy life:
1, try to eat less barbecue food.
In view of the ubiquitous heterocyclic amines in daily barbecue food, it is difficult to completely remove them, and it is impossible to completely prevent people from ingesting such mutagenic and carcinogenic substances in real life. Therefore, it is recommended to eat barbecue food as little as possible. In addition, methods to avoid excessive heterocyclic amines are:
(1) when frying meat products, the oil temperature should be controlled so as not to produce a large amount of oil smoke. The cooking oil used for frying should be replaced regularly, because many ingredients beneficial to human body, such as vitamins, can be oxidized and volatilized in the process of high temperature heating, and the nutrition is completely lost; At the same time, unsaturated fatty acids and other compounds in cooking oil will undergo various reactions such as polymerization, forming fatty acid polymers and other substances harmful to human body.
② The time for frying and grilling should not be too long, and it is necessary to avoid frying and grilling meat products, because it will form more heterocyclic amines. Hanging a layer of starch paste on the outside of fried meat products before frying can effectively prevent the formation of heterocyclic amines.
③ When eating barbecue food, some vegetables and fruits, such as citrus, seabuckthorn, hawthorn, green pepper, tomato and cabbage, are rich in vitamin C, which can inhibit the toxicity of heterocyclic amines.
2. Eat pickled food reasonably.
The transformation of nitrite produced in the curing process of meat and vegetables into nitrosamines is its main harm. The following three points should be paid attention to when curing and eating this kind of food:
① Salt plays an antibacterial and antiseptic role in the process of curing food. When the concentration is 10~ 15%, only a few bacteria grow, and when the concentration exceeds 20%, almost all microorganisms will stop growing. Therefore, increasing the amount of salt (more than 10%) and prolonging the curing time (more than 20 days) can reduce bacterial reproduction and nitrite content. Generally speaking, pickled sauerkraut and pickles preserved for more than one month are basically safe.
② When curing bacon, sausage, sauerkraut and pickles at home, we should pay attention to the amount of nitrite added. Reference can be made to China's standard for nitrite consumption in meat products (less than 0. 15g/kg).
③ Use foods that decompose nitrite and inhibit nitrosamine toxicity. For example, allicin in garlic can inhibit nitrate-reducing bacteria in the stomach and significantly reduce the nitrite content in the stomach; Tea polyphenols in tea can block the formation of nitrosamines; Fruits and vegetables rich in vitamin C can prevent the formation of nitrosamines in the stomach and inhibit the mutagenicity of nitrosamines.
3. Treat overnight food correctly
Eating overnight food is harmful to human body to some extent, so we should have a correct attitude towards overnight food.
(1) Cooking and entertaining guests should be "tailored", with appropriate amount, cultivate good eating habits, and avoid harmful substances such as nitrite in overnight food from entering the human body.
(2) All kinds of vegetables contain nitrite in different degrees during the process of placing after heating, and the nitrite content of stem and leaf vegetables, especially Chinese cabbage and spinach, is more than that of melon vegetables after cooking; And the longer the storage time, the higher the nitrite content. Therefore, fresh vegetables should be fried and eaten as soon as possible.
③ Considering that the nitrite formed by the leftover food stored at low temperature is much less than that stored at room temperature, the leftover food must be put in the refrigerator in time and should not be stored for too long. When the food is taken out of the refrigerator, it must be thoroughly heated to prevent bacterial food poisoning.
In short, we think it is not advisable to eat barbecue, pickled food and leftover food for a long time. We advocate reasonable cooking and eating habits, eat less fried, fried, roasted and pickled food, avoid overnight meals, and eat more foods rich in vitamins, not to prohibit people from eating these foods. Because the harm caused by food safety is related to the dose of substances ingested in the body, as long as the intake of harmful substances is reduced, the risk of harmful substances can be reduced. In addition, there are many unreasonable eating habits and methods in daily life, and the chemical nature of their health problems is also different. In this paper, the chemical and health problems exposed by barbecue, pickling and overnight food are discussed, with the aim of attracting jade, so that people can learn the chemical mechanism and harm of food-borne harmful compounds, eat scientifically and live healthily.