Nutritious food additive

Nutritious food additives (12 points)

Pears, apples, bananas, potatoes and other fruit and vegetable juice is very easy to change color. After changing the color is not only ugly, the taste is also affected. How to do? Add a little lemon juice.

In fruits and vegetables, there are many different polyphenol compounds. After peeling, these compounds have been exposed in the air oxidation, formation of quinone compounds (k game n). This kind of compound is easy to connect with each other, become "brown pigment", so that these foods. And lemon juice contains a lot of ascorbic acid, it can put the reduction of quinone as the initial of polyphenols in the state; also can be directly oxidized, to consume the oxygen around the polyphenols, in order to protect the polyphenols from oxygen attack. In this way, ascorbic acid at the expense of the self, to protect the fragile polyphenols, to maintain the fruits and vegetables "fresh" color.

In the food industry, according to the mechanism of the action of lemon juice, can be directly added ascorbic acid. In the supermarket sales of fruit juice and vegetable juice, a lot of wine added ascorbic acid, in order to maintain its appearance and flavor.

The role of ascorbic acid not only this. People often joined the nitrite in cooked meat products. Nitrite has two functions: one is reaction with myoglobin to appear attractive red; the second is inhibit bacterial growth, realize the function of anticorrosion. Adding ascorbic acid can promote the previous reaction, thus speeding up the process of "hair color". Many people believe that nitrite is a kind of carcinogen ". In fact, it itself does not cause cancer, only when it is associated with the amino acid in the meat, the formation of the nitrite is a carcinogen. If ascorbic acid is added to the meat, it will inhibit the occurrence of the transformation process, thereby reducing the nitrite "may" carcinogenic risk. In the need for nitrite in meat, and sometimes to join the ascorbic acid. Because of the fat oxidation in meat will release a bad taste, which is commonly referred to as rancid taste". If added ascorbic acid, it would pre empt consumption around the oxygen, thereby protecting the oil is not oxidized, help to keep the meat fresh.

The ascorbic acid itself is easily oxidized, generation of deoxy ascorbic acid. The DNA of ascorbic acid are not willing to "black sheep", will to win others to rebuild the hydrogen atom. People use this feature in the pasta processing, often adding ascorbic acid, improve dough properties, increase the dough out. Flour contains gluten, of which there are many thiol (be it based -- that is, with a sulfur atom of a hydrogen atom, ascorbic acid deoxidizing will plunder the hydrogen atom. When we rub the surface, the hydrogen atoms in the thiol group will be taken away by the hydrogen, and the remaining sulfur atoms will be connected to two two, forming a so-called two sulfur bonds. When the two disulfide bond formation in large, gluten dough will form a huge network, thereby enhancing its taste.

Sixthly, in most cases, food additives is to improve the flavor, taste, increase food stability and so on, itself does not have a nutritional significance. But ascorbic acid does not belong to this "most". When it is used as a food additive, it is usually called "ascorbic acid". And it is also the human body needs nutrients - vitamin C. Vitamin C is not stable, air, light, heat, contact with the metal container, it will make it lose activity or decomposition. However, it is not stable, so it has a good "anti oxidation". In the body, it protects cells from oxidative damage. Added to the food, it is first oxidized to protect self sacrifice, other ingredients in food.

From the "food and life" (title)

12 title "nutritious food additives" in the text specifically refers to what? Why does it have nutrition? Please specify. (3 points)

Please read the article 13 paragraph carefully, in the following lines fill in the appropriate content. (2 points)

Ascorbic acid added to the join mechanism of nitrite in cooked meat products is: can, can inhibit the nitrite and meat amino acid reaction nitrosamines this conversion process occurs.

14 contact context, please talk about the expression of the following sentences in the expression of the effect. (2 points)

The DNA of ascorbic acid are not willing to "black sheep", will to win others to rebuild the hydrogen atom.

15 what is the method used in the first part of this article? What is the role? (2 points)

16 it is generally believed that food additives are harmful to human beings, to talk about "agent" pale. Read this article, you have a kind of understanding of food additives and their use? Please talk about the contents of the article. (3 points)

12 (3 points) of ascorbic acid. (1 points) is the human body needs nutrients of ascorbic acid (vitamin C, cooco.net.cn well test

1) it has good oxidation resistance, protect the body cells from oxidative damage. (1 points)

13 (2) to promote and accelerate the reaction of nitrite myoglobin, the "color" process.

14. (2) "Prodigal" using metaphor (1) vividly illustrates the ascorbic acid is easily oxidized, so as to generate a substance of dehydroascorbic acid. (1 points)

15 (2 points) for example, the specific description of the ascorbic acid as a food

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