Nutritious food additives

Yuan Wuxin

① Fruit and vegetable juices such as pears, apples, bananas, and potatoes can easily change color. The discoloration is not only unsightly, but the taste is also affected. What to do? Add some lemon juice.

② Fruits and vegetables contain varying amounts of polyphenol compounds. After peeling, these compounds are exposed to air and oxidized to form quinone (kūn) compounds. This quinone compound easily connects to each other and becomes the "brown pigment" that gives these foods their color. Lemon juice contains a large amount of "ascorbic acid", which can reduce quinones to their original polyphenol state; it can also be directly oxidized, thereby consuming the oxygen around the polyphenols, thereby protecting the polyphenols from oxygen attack. In this way, ascorbic acid sacrifices itself to protect fragile polyphenols and maintain the "fresh" color of fruits and vegetables.

③In the food industry, people can directly add ascorbic acid according to the mechanism of lemon juice. Many of the fruit and vegetable juices sold in supermarkets have ascorbic acid added to preserve their appearance and flavor.

④The role of ascorbic acid goes beyond this. Nitrite is often added to cooked meat products. Nitrite has two functions: first, it reacts with myoglobin to make it appear attractive red; second, it inhibits bacterial growth and achieves antiseptic function. Adding ascorbic acid can promote the previous reaction, thereby speeding up the "color development" process. Many people believe that nitrite is a "carcinogen." In fact, it itself is not carcinogenic. Only when it reacts with the amino acids in meat, the nitrosamines generated are carcinogens. If ascorbic acid is added to meat, it inhibits this conversion process from occurring, thereby reducing the "possible" carcinogenic risk of nitrites. Ascorbic acid is sometimes added to meat products that do not require nitrite. Because the oxidation of the fat in the meat will release a bad taste, which is commonly known as the "hala taste". If ascorbic acid is added, it will consume the surrounding oxygen first, thereby protecting the oil from oxidation and helping to keep the meat flavor "fresh".

⑤ Ascorbic acid itself is easily oxidized to generate deoxyascorbic acid. These deoxyascorbic acids are not willing to "squander" and will seize other people's hydrogen atoms to rebuild their homes. People take advantage of this characteristic and often add ascorbic acid in pasta processing to improve dough properties and increase dough texture. Flour contains gluten, which contains many sulfhydryl (qíu) groups - sulfur atoms with a hydrogen atom. Deoxyascorbic acid will rob the hydrogen atom. When we knead dough, the hydrogen atoms in the thiol groups are taken away by deoxyascorbic acid, and the remaining sulfur atoms are connected two by two to form a so-called disulfide bond. When a large number of disulfide bonds are formed, the gluten proteins in the dough form a huge network, thus strengthening its chewiness.

⑥In most cases, food additives are used to improve flavor, taste, increase food stability, etc., and do not themselves have nutritional significance. But ascorbic acid does not belong to this "majority." When used as a food additive, it is often called "ascorbic acid." And it itself is also a nutrient needed by the human body-vitamin C. Vitamin C is unstable. Air, light, heating, and contact with metal containers will cause it to lose activity or decompose. However, it is this instability that gives it good "antioxidant properties." In the body, it protects cells from oxidative damage. When added to food, it is oxidized first, thereby protecting other ingredients in the food.

--Excerpted from "Food and Life" (edited)

1. What does the title "Nutritious food additives" refer to in the article? Why is it said to be nutritious? Please be specific. (4 points)

2. Please read paragraphs ②-④ carefully and fill in the appropriate content on the following lines. (4 points)

(1) The mechanism of ascorbic acid added to fruit and vegetable juices is: it can reduce quinones to their original polyphenol state; it can also

(2) Added ascorbic acid The mechanism of action in cooked meat products added with nitrite is: It can inhibit the conversion process of nitrite-amino acid reaction in meat to produce nitrosamines.

3. Based on the context, please tell me the meaning and function of the words in the following sentences. (4 points)

(1) If ascorbic acid is added to meat, it will inhibit the occurrence of this conversion process, thereby reducing the "possible" carcinogenic risk of nitrite.

(2) These deoxyascorbic acids are not willing to "squander" and will seize other people's hydrogen atoms to rebuild their homes.

4. What explanation method is used in paragraph ③ of this article? What is its effect? ??(3 points)

5. People generally believe that food additives are harmful to the human body. The "agent" changes color. After reading this article, what kind of understanding do you have about food additives and their use? Please talk about it based on the content of the article. (4 points)

Answer:

1. (4 points) refers to ascorbic acid. (2 points) Ascorbic acid is vitamin C, a nutrient needed by the human body. (1 point) It has good antioxidant properties and protects cells in the body from oxidative damage. (1 point)

2. (4 points) (1) Directly oxidized, consuming the oxygen around the polyphenols and protecting the polyphenols from oxygen attack; (2 points) (2) Promoting sub-oxidation Nitrates react with myoglobin to speed up the "color development" process. (2 points)

3. (4 points) (1) "Possibly" indicates uncertainty, indicating that nitrite itself is not carcinogenic, only when it reacts with amino acids in meat to form nitrite There is a risk of cancer only when amines are present. (1 point) Reflects the accuracy of expository language. (1 point)

(2) "Prodigal" uses metaphor, (1 point) vividly illustrates that ascorbic acid is easily oxidized, thereby producing a substance-dehydroascorbic acid. (1 point)

4. (3 points) Give an example, (1 point) specifically illustrate that ascorbic acid is widely used and has great effects as a food additive. (2 points)

5. (4 points) Not all food additives are harmful. Some food additives have nutritional value, and some food additives can improve flavor and taste, and increase video stability. It is not necessary Talk about the color change of "agent". (2 points) Food additives are harmless to the human body as long as they are used rationally. (2 points) (If you answer that food additives are harmful, no points will be given)