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Why do apples turn yellow after being cut?

2, (such as potatoes, eggplant, etc. ) This is also the case. Browning affects the appearance of food and reduces the nutrients in the outer layer, but it is still edible. If the apple is peeled and left for a long time, the oxidative decomposition of plant cells in the air will be intensified, and the nutrients in the outer layer of the apple will be decomposed more. Pectin will be further decomposed into pectin and methanol under the action of enzymes, which will make the pulp loose, wet, discolored, stale and even rotten.

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Why does the surface of apples turn yellow after being cut for a period of time?

When the apple is peeled or cut for a period of time, the color of the cut surface will change from light to dark, and finally to dark brown. The discoloration reaction is mainly due to the presence of phenolic compounds in these plants. For example: polyphenols, catechol, etc. Phenolic compounds are easily oxidized to quinones, that is, they change color to yellow, and the color gradually deepens with the increase of reaction amount, and finally becomes dark brown. The oxidation reaction is due to contact with oxygen in the air, and phenol oxidase is released from cells. Before tissue damage, phenol oxidase existed in organelles, which could not contact with phenolic compounds and oxygen in the air could not enter, so there was no oxidative discoloration reaction. When the cell tissue is damaged, the released phenol oxidase contacts with phenolic compounds, which catalyzes the oxidation of phenolic compounds. Under the action of oxygen in the air, a discoloration reaction will occur. Among them, polyphenols can be directly oxidized to quinones and change color. Catechol molecules are polymerized by phenol oxidase. Two catechol molecules are linked together to form a catechol dimer, which can be linked in pairs to form a tetramer. Single catechol molecule and its dimer and tetramer are colorless, but catechol tetramer can form polymer, which is purple. Therefore, the more polymer is formed, the darker the incision surface is. After the apple changes color, the content of vitamin C will decrease, which will affect the nutritional value. In order to prevent the cut apples from discoloring, they may not be in contact with air. The best way is to soak apples in salt water. Let the cut apples not change color. The cut apples will soon be dull in color, which will affect the appearance. Is there any clever way to change it? It's simple. Drop some lemon juice on the cut surface of the apple to keep the color unchanged and the original flavor. Other fruits that change color easily can also be treated in this way, and the effect is good!

Browse11132017-11-26

Why do apples turn yellow when cut for a long time?

Apples contain a lot of vitamin C, also called L- ascorbic acid, which is an antioxidant and easily oxidized. The apple was wrapped in a leather bag. Once cut or bitten, the vitamin C in their juice will be rapidly oxidized to oxidized vitamin C, so it will turn yellow, but it should gradually turn black after being put away. There are ways to prevent it. Drop some lemon juice on the cut surface of the apple to keep the color unchanged and the original flavor. Other fruits that change color easily can also be treated in this way, and the effect is good!

259 browse19822017-09-16

Why does the bitten part of the apple change color after a bite?

Cause of discoloration: Apple contains an oxidase. After peeling the apple, the air meets the pulp, and the organic matter in the pulp oxidizes and discolors under the catalysis of oxygen enzymes, and the apple turns ugly dark brown. It can also be said that when the apple is peeled or cut for a period of time, the color of the cut surface will change from light to dark, and finally become dark brown. Not only apples, but also potatoes, peaches and eggplant. It will also change color after being cut. What's going on here? The discoloration reaction is mainly due to the presence of phenolic compounds in these plants. For example: polyphenols, catechol, etc. Phenolic compounds are easily oxidized to quinones, that is, they change color to yellow, and the color gradually deepens with the increase of reaction amount, and finally becomes dark brown. The oxidation reaction is due to contact with oxygen in the air, and phenol oxidase is released from cells.

Browse 9355 20 17-09-29

Why do apples turn yellow after a period of time?

The yellowing of apples is mainly caused by oxidation. Apple contains many substances such as fruit acid and malic acid, which are easily oxidized in the air. After being oxidized, apples will turn yellow or dark reddish brown. So apples can't be kept in the air, especially those that have been opened. So if you don't want to eat apples right away, you can soak them in water or wrap them in plastic wrap and put them in the refrigerator. This can prevent oxidation. When the apple is peeled or cut for a period of time, the color of the cut surface will change from light to dark, and finally to dark brown. The discoloration reaction is mainly due to the presence of phenolic compounds in these plants. For example: polyphenols, catechol, etc. Phenolic compounds are easily oxidized to quinones, that is, they change color to yellow, and the color gradually deepens with the increase of reaction amount, and finally becomes dark brown. The oxidation reaction is due to contact with oxygen in the air, and phenol oxidase is released from cells.

Browse 2553 20 18-07- 18.

Why do apples turn yellow after being cut for a period of time?

When apples are peeled, phenolic compounds in plant cells will undergo oxidation reaction with air under the action of phenolase, producing a large number of quinones. Neoquinones can make plant cells turn brown quickly, which is called enzymatic browning of food. So apples will change color after peeling for a period of time. Not only apples, pears and some vegetables (such as potatoes, eggplant, etc. ) This is also the case. Browning affects the appearance of food and reduces the nutrients in the outer layer, but it is still edible. If the apple is peeled and left for a long time, the oxidative decomposition of plant cells in the air will be intensified, and the nutrients in the outer layer of the apple will be decomposed more. Pectin will be further decomposed into pectin and methanol under the action of enzymes, which will make the pulp loose, wet, discolored, stale and even rotten.

85 Browse 1780 20 16-07-03