Some foods contain trans fatty acids:
Trans fatty acids exist in 1, beef and mutton, dairy products, fruits and vegetables.
2, vegetable cream, potato chips, salad dressing, biscuits, cakes, bread, cookies, ice cream, French fries, etc.
3, foreign fast food such as French fries, fried chicken legs.
4. There are many solidified oils, and hydrogenated oils in food contain trans fatty acids.
5. Vegetable oil after high temperature heating: Because vegetable oil usually needs high temperature above 250℃ and heating time of 2 hours in the process of refining and deodorization. Due to high temperature and long-term heating, a certain amount of trans fatty acids may be produced. Generally, beef fat contains 2.5% ~ 4%, milk fat contains 5% ~ 9.7%, margarine contains 7. 1% ~ 17.7% (the highest is 3 1.9%), and shortening contains 10.3% (the highest is 31.
Percentage of trans fatty acids in total fatty acids.
3% ~ 5% of milk and goat's milk
The body fat of ruminants is 4% ~ 1 1%
Hydrogenated vegetable oil 14.2% ~ 34.3%
Shorten oil by 7.3% ~ 3 1.7%
Hard butter 1.6% ~ 23. 1%
Bread and Danish cake 37%
Fried chicken and French fried potatoes 36%
French fries 35%
Candy fat 27%
The Management Standard of Food Nutrition Labeling issued by the Ministry of Health in June 5438+February 2007 stipulates that when the trans fatty acid content in food is ≤0.3g/ 100g, it can be marked as 0. This is why some food ingredients lists clearly contain non-dairy creamer and hydrogenated oil, but the labels indicate that trans fat is 0. Be careful when buying food in the future. Foods marked with trans fat 0 do not necessarily contain trans fat.
In daily life, there are many foods containing trans fatty acids, such as cakes, cakes, biscuits, bread, Indian bread, salad dressing, French fries, potato chips, popcorn, chocolate and ice cream. Egg yolk pie ... all soft, sweet and unique oily foods (vegetable butter, margarine, etc. ) contains trans fatty acids. The reason is that vegetable oil can also produce trans fatty acids when it is used for catalytic hydrogenation to produce fat.
Generally speaking, oily foods that taste fragrant, crisp and slippery may use partially hydrogenated vegetable oil, and foods rich in hydrogenated vegetable oil may contain trans fatty acids. Such as biscuits, chocolate pie, egg yolk pie, pudding cake, candy, ice cream and so on. There are also fast food restaurants and western fast food restaurants that often use hydrogenated oil. We should pay special attention to the milk tea made and sold now, because it needs hydrogenated vegetable oil because of its "emulsified" and "smooth" state characteristics.
Trans fats used by humans mainly come from partially hydrogenated vegetable oils. Hydrogenation is a food industry technology invented in the early 20th century. Hydrogenation of edible oil was invented by German chemist William Norman and patented in 1902. 1909, Procter & Gamble Company of the United States obtained the right to use this patent in the United States, and began to promote the first semi-solid ghee product made entirely of vegetable oil in191.
Compared with ordinary vegetable oil, hydrogenated vegetable oil is more stable and solid, which can make food look better and taste softer. Compared with animal oil, the price is lower, and at the beginning of the 20th century, people thought that vegetable oil was healthier than animal oil. Replacing animal oil with cheap and "healthy" hydrogenated vegetable oil was considered an improvement at that time. Before the invention of hydrogenated vegetable oil, the shortening used to soften the taste in food processing was lard, which was later replaced by hydrogenated vegetable oil.
Hydrogenation of vegetable oil can convert cis-unsaturated fatty acids into solid trans-fatty acids which are more stable at room temperature. Manufacturers use this process to produce margarine, and also use this process to increase the shelf life of products and stabilize the flavor of food. Trans fatty acids produced by hydrogenation of unsaturated fatty acids account for 8%-70%.
Trans fatty acids also exist in nature. When unsaturated fatty acids are digested by ruminants (such as cattle), fatty acids are partially hydrogenated by bacteria in the rumen of animals. Trans fatty acids exist in the fat of milk, dairy products and beef and mutton, accounting for about 2%-9%. Chickens and pigs also absorb trans fatty acids through feed, so trans fatty acids enter pork and poultry products.
According to the data of the Ministry of Health, the average daily intake of trans fatty acids in China is 0.6 grams. Li Zaigui, an expert in food science and nutrition at China Agricultural University, believes that this data is worth analyzing. "The base includes a large number of rural people, but they rarely eat cakes, drink coffee and eat egg yolk pie, so there are few opportunities to contact trans fatty acids. In the urban population, some people's daily intake may far exceed the international standard, that is, 2-3 grams. " "For example, if the oil content of a biscuit is 20%, and you eat 100 grams of biscuits, according to the average level of trans fatty acids accounting for 20% of the total oil content, there may be 4 grams of trans fatty acids."
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Trans fatty acids (TFA), also known as trans fats, are called "time bombs on the table". The main source of TFA is partially hydrogenated vegetable oil. Partially hydrogenated oil has the advantages of high temperature resistance, no deterioration and long storage time, and is widely used in cakes, biscuits, quick-frozen pizza, French fries, popcorn and other foods. Excessive intake of trans fatty acids will increase blood cholesterol, thus increasing the risk of cardiovascular disease.
On June 6, 20 15, the US Food and Drug Administration announced that it would completely ban the use of artificial trans fats in food within three years to help reduce the incidence of heart disease.
Fatty acid is a kind of carboxylic acid compound, which is composed of hydrocarbon group and carboxyl group. Fat is a triacylglyceride composed of glycerol and fatty acids. These fatty acid molecules can be saturated, that is, all carbon atoms are interconnected, and saturated molecules are solid at room temperature. When carbon atoms in the chain are connected by double bonds, fatty acid molecules can be unsaturated. When a double bond is formed, the chain has two forms: cis and trans. The cis bond looks like a U-shape, and the trans bond looks like a line. Unsaturated fatty acids formed by cis bonds are liquids such as vegetable oils at room temperature, while unsaturated fatty acids formed by trans bonds are solids at room temperature.
Trans fatty acids (TFA) exist naturally and are manufactured artificially. Trans fatty acids naturally exist in human milk and milk. Trans fatty acids in milk account for about 4-9% of total fatty acids, and human milk accounts for about 2-6%.
Trans fatty acids are unsaturated fatty acids produced in the process of hydrogenation modification of vegetable oils (modified oils are called hydrogenated oils). This processing can prevent the oil from deteriorating and change the flavor. Trans fatty acids contain at least one trans structure double bond fatty acid, that is, C=C bonded hydrogen is on both sides, while C=C bonded hydrogen in cis structure fatty acids is only on the same side.
Trans fatty acids are unsaturated fatty acids with trans double bonds. The two hydrogen atoms combined by two carbon atoms on the double bond are on both sides of the carbon chain, and their spatial conformation is linear, corresponding to cis fatty acids. The two hydrogen atoms combined by two carbon atoms on the double bond are on the same side of the carbon chain, and their spatial conformation is curved. Because of their different three-dimensional structures, first, their physical properties are different, such as cis-fatty acids are mostly liquid and have low melting points; TFA is mostly solid or semi-solid with high melting point. Secondly, their biological functions are far from each other, mainly manifested in the interference of TFA on polyunsaturated fatty acid metabolism, the influence on blood lipid and lipoprotein, and the inhibition on fetal growth and development.
Trans fats are produced in the process of partial hydrogenation of vegetable oils. With the help of a small amount of catalytic metals such as nickel, palladium, platinum or cobalt, hydrogen is added to vegetable oils. With the progress of hydrogenation, the content of trans fatty acids will decrease. If hydrogenation can be completed, trans fatty acids will not remain, but the oil at the end of the reaction will have no practical use value because of its excellent quality.
Main danger
Trans fat is the abbreviation of a large class of fatty acids containing trans double bonds.
Many epidemiological investigations or animal experiments have studied various possible hazards of trans fats, among which the impact on cardiovascular health is the strongest and widely accepted.
The regulations of trans fats by WHO and national authorities are also based on their effects on cardiovascular health. For example, WHO recommends that the daily calories from trans fats should not exceed 65,438+0% of the total calories of food (roughly equivalent to 2 grams). China uses this indicator for evaluation, and countries such as Britain and France use 2% as the recommendation standard. What needs to be pointed out in particular is that this is not a "safety standard" but only a "guiding opinion". It doesn't mean that more than this amount is "harmful" and less than this amount is "safe", but "the risk it brings is acceptable" Our goal should also be "the lower the better".
However, the relationship between intake and coronary heart disease risk varies from study to study. The most risky conclusion is that the ratio of trans fat calories to total food calories "will double the incidence of coronary heart disease for every 2 percentage points increase". Other studies have shown that the risk is much smaller than this. Moreover, "double occurrence risk" is a relative proportion, and the specific risk depends on the actual occurrence rate, such as from 0. 1% to 0.2%, much lower than from 1% to 2%.
As for the correlation between trans fats and diseases affecting early growth and development, type II diabetes, hypertension and cancer, there is no clear evidence to prove it.
Control measure
Some Japanese, Hongkong and Taiwan Province media and websites mentioned the health effects of trans fats. But generally speaking, there is not much concern about the legislation of trans fat ban in Asia. There are still a large number of processed foods containing trans fats on the market.
The Department of Health of the Executive Yuan of Taiwan Province Province stipulates that the nutrition labels of packaged foods in the market should be marked with saturated fat and trans fat from June 5438+1 October1day, 2008.
At the two sessions in China in 2008, members of Hangzhou CPPCC submitted a proposal on restricting the sale of carbonated drinks and high-calorie and high-fat snacks in primary and secondary schools. The proposal suggests restricting snacks and drinks rich in trans fats.
201March 18, the national food safety risk assessment center released a message that trans fatty acids known as "time bombs on the table" were exaggerated. The intake of trans fatty acids in the daily diet of residents in big cities such as Beijing and Guangzhou is only 0.34%, which is far below the limit of 1% recommended by the World Health Organization.
European and American countries have imposed legislative restrictions on artificial fat. In Europe, since June 1 2003, any oil containing more than 2% artificial fat in the Danish market has been banned, so Denmark became the first country in the world to establish laws and regulations on artificial fat. Since then, the Netherlands, Sweden, Germany and other countries have also set the limit of artificial fat in food, and at the same time require food manufacturers to add the content of artificial fat in nutrition labels. In 2004, the US Food and Drug Administration (FDA) also stipulated that from 2006, the content of artificial fat should be added to the column of "nutritional ingredients" on all food labels. The FDA also reminds people to eat as little artificial fat as possible.
At the same time, foreign companies have seen the "anti-artificial fat wind" in Europe and America, and have introduced new products to replace artificial fat. For example, a Finnish food company developed a new method to produce vegetable butter with high phytosterol content, while a Swedish margarine manufacturer successfully developed a new lipase as an artificial fat substitute to remove the ingredients containing artificial fat. In the United States, Lipton, Nestle and other companies have also reduced or even removed artificial fats in some foods.
The US Food and Drug Administration requires foods to clearly list trans fats in food packaging. With more and more studies pointing out that trans fats are harmful to health, some food manufacturers such as Kraft and KFC filed lawsuits involving the use of trans fats, and restaurants, supermarkets and governments in the United States, Canada and Britain began to stop using trans fats in food production and processing. Please refer to the English version for details.
In 2003, Denmark legislated for the first time to ban the sale of ingredients with trans fat content exceeding 2%. Natural trans fats are not affected by law.
On June 30, 2006, new york held a hearing on this issue, and the Municipal Health Commission finally decided that from July 1 day, 2008, the artificial trans fat used in each serving of food in restaurants in the city should not exceed 0.5g.
On June 5438+ 10, 2008, Calgary, Canada decided that the trans fat content in the oil used by restaurants and fast food restaurants should not exceed 2%.
In April 2008, Switzerland followed Danish legislation to restrict the sale of trans-fat foods.
In July, 2008, Arnold Schwarzenegger, the governor of California, signed a bill to ban the use of trans fats in restaurants in the state, which will take effect on 20 10.
United States of America
In 2005, a non-profit organization in the United States, which promoted the prohibition of trans fats, sued Kraft Foods, demanding that the company stop using trans fats in Oreo biscuits. After Kraft Foods agreed to find a substitute for trans fats, the organization withdrew its complaint. In 2006, the Center for Public Interest Science, a non-profit organization in Washington, accused KFC of using trans fats in food cooking. In 2006, KFC announced that it would replace trans fats used by American chain stores in this restaurant with soybean oil by April 2007. Its Canadian restaurant chain has also announced similar measures.
On June 5438+ 10, 2007, McDonald's announced that its French fries in American chain stores were being fried with non-trans fat, and if the effect was good, it would be popularized throughout the United States.
Facing the criticism of the Center for Public Interest Science in May 2007, Burger King announced that it would switch to non-trans fats in all its branches in the United States from the end of 2008.
2013165438+17 October, the US Food and Drug Administration announced that based on the existing scientific evidence and the conclusions of the expert committee, it had initially decided to ban artificial trans fats harmful to human health.
20 10, 1 1, the Ministry of Health of China officially responded to the issue of trans fatty acids. Deng Haihua1October 9, a spokesman for the Ministry of Health, said that the Ministry of Health has organized the risk monitoring and assessment of trans fatty acids, and will organize the preparation and revision of relevant standards according to the national food safety standard procedures on the basis of risk assessment.
Zhang Jian, a researcher at the Institute of Nutrition and Food Safety of China CDC, said that in 2003, the Institute of Nutrition and Food had carried out the monitoring of trans fatty acids in food in China. The preliminary monitoring results show that the per capita intake of trans fatty acids in China is about 0.6 grams, far below the level reported by European and American countries. In Dietary Nutrition and Chronic Diseases (2003 edition), WHO and FAO suggested that "the maximum intake of trans fatty acids should not exceed 1% of total energy". Zhang Jian said that the conversion of this 1% is about 2 grams per person per day.
On 20th12, the Ministry of Health of China issued the national food safety standard "General Principles of Nutrition Labeling in prepackaged foods", with the number of GB 28050-20 1 2, in which four mandatory labels stipulate that "food raw materials are contained or hydrogenated and/or used in the production process, and in addition, D.4.2 stipulates that" the daily intake of trans fatty acids shall not exceed. The intake of trans fatty acids should be less than 1% of the total daily energy, which is harmful to health. Excessive intake of trans fatty acids will increase blood cholesterol, thus increasing the risk of cardiovascular disease. "The national standard will be officially implemented on 20 13 10 1.