Why do apples turn yellow when cut? Why do apples turn yellow after cutting, and some do not turn ye

When the apple is peeled or cut and left for a while, the color of the cut surface will change from light to dark and finally dark brown. The discoloration reaction occurs mainly due to the presence of phenolic compounds in these plants. For example:

Polyphenols, catechols, etc. Phenolic compounds are easily oxidized to quinones, that is, they change color and turn yellow, and the color gradually deepens with the increase of the amount of reaction, and finally turns dark brown. The oxidation reaction occurs due to the contact with oxygen in the air and the release of phenol oxidase in the cell.

Phenolic oxidase exists in organelles and cannot come into contact with phenolic compounds until the tissue is damaged, and oxygen in the air cannot enter, so no oxidative discoloration reaction occurs. When the cell tissue is damaged, phenol oxidase is released to contact with phenolic compounds, catalyzing the oxidation of phenolic compounds, coupled with 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, on the other hand, polymerize under the action of phenol oxidase. Two catechol molecules are linked together to form catechol dimers, which in turn can be joined in pairs to form tetramers. The individual catechol molecules and their dimers and tetramers are all colorless, but catechol tetramers can form multimers, which are purple.

So the more polymers are formed, the darker the color of the incision surface will be. When apples change color, the amount of vitamin C will decrease, affecting the nutritional value. To prevent the apple from changing color after cutting, the best way to keep it out of contact with the air is to soak the apple in salt water.

Let the cut apple not change color The color of the cut apple will quickly dull and affect the appearance, is there any trick to change it? It's as simple as dripping lemon juice on the cut side of the apple, which not only does not change color, but also retains the original flavor. In addition, some fruits that are easy to change color can also be treated in this way, and the effect is excellent!

The iron element in it is oxidized.

Ferric iron is easily oxidized by oxygen in the air to trivalent iron, which is yellow.

When the apple is peeled, the phenolic substances in the plant cells are oxidized with the air under the action of phenolase, producing a large amount of quinones, causing the apple to turn yellow.

Neoquinones can cause plant cells to turn brown quickly. This change is known as enzymatic browning of food. Therefore, after the apple is peeled, it will change color after leaving it for a while. It's not just apples, pears, and some vegetables (like potatoes, eggplant, etc.). This is also the case.

Browning in this process affects the appearance of the food, lowering the nutrient content of the outer layer, but it is still edible. If the apple is stored for a long time after peeling, the oxidative decomposition of plant cells in the air is intensified, the nutrients in the outer layer of the apple are decomposed more, and the pectin substances are further decomposed into pectin acid and methanol under the action of enzymes, making the flesh loose, moist, discolored, tasteless and even rotten.

The divalent iron in apples is oxidized.

Oxidized by oxygen in the air.

Summary. Dear, I'm honored to have your question The information that the teacher found for you here is: Why do apples turn yellow after cutting, and some are not yellow:

Apples will turn yellow after cutting, and some are not yellowish because when apples are peeled, the phenols in plant cells are oxidized with the air under the action of phenols, producing a large number of quinones. The new quinones can cause plant cells to turn brown quickly, a change called enzymatic browning of food, so apples will change color after peeling and leaving for a while. This is also the case for apples and pears, as well as some vegetables (such as potatoes and eggplants).

This browning affects the appearance of the food, reducing the nutrient content of the outer layer, but it is still edible. If the apple is left for a long time after peeling, the oxidative decomposition of plant cells in the air is intensified, the nutrients in the outer layer of the apple are decomposed more, and the pectin substances are further decomposed into pectic acid and methanol under the action of enzymes.

Why do apples turn yellow after cutting, and some do not turn yellow

Dear, I'm honored to have your question The information that the teacher found for you here is: why do apples turn yellow after cutting, and some do not turn yellow: apples will turn yellow after cutting, and some do not turn yellow because when apples are peeled, the phenols in plant cells will oxidize with the air under the action of phenols, producing a large number of quinones.

The new quinones can cause plant cells to turn brown quickly, a change called enzymatic browning of food, so apples will change color after peeling and leaving for a while. This is also the case for apples and pears, as well as some vegetables (such as potatoes and eggplants). This browning affects the appearance of the food, reducing the nutrient content of the outer layer, but it is still edible.

If the apple is left for a long time after peeling, the oxidative decomposition of plant cells in the air is intensified, the nutrients in the outer layer of the apple are decomposed more, and the pectin substances are further decomposed into pectic acid and methanol under the action of enzymes.

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1. Whether it is cut from the middle or peeled the apple, it will cause the phenolic substances in the apple cells to oxidize with the air under the action of enzymes, and quinones will appear. The emergence of new quinones causes plant cells to turn brown, a reaction known as enzymatic browning of food.

With the extension of time, the plant cells in the apple will be further oxidized, the nutrients will be more decomposed, and pectal acid and methanol will appear under the action of enzymes, which is also what we found that the apple tastes after being cut and stored for a period of time, and the color becomes darker and darker, and finally rots.

2 This should be judged according to the time, generally speaking, after the incision, the cut will appear yellow, and the longer the time, the darker the color. Of course, if it is still safe to eat half an hour after cutting, and the flesh inside is not corroded and infected, you can wash it and continue to eat, or you can cut off the yellowed side and eat it again.

3 grams of dietary fiber in the peel of a medium-sized apple. After peeling, the dietary fiber in apple flesh is only grams.

Medium-sized apples contain milligrams of vitamin C and 98 international units (IU) of vitamin A in their skin. After peeling, apple pulp contains only milligrams and 61 IU of these two vitamins.

Apple peels are rich in the natural antioxidant quercetin, which protects the lungs from pollutants. Eating at least 5 apples a week with the skin on the skin can improve lung function.

Quercetin, an antioxidant rich in apple peels, helps protect memory by helping to prevent brain tissue damage associated with degenerative diseases such as Alzheimer's disease (Alzheimer's disease).

Apple peel has good anti-cancer and anti-cancer effects. Researchers have identified more than a dozen triterpenoid compounds from apple peels, all of which inhibit the growth of cancer cells such as liver, colon or breast cancer, and also kill cancer cells.

Apples are high-fiber, low-calorie foods, and regular eating is not easy to feel hungry and has less calorie intake, which helps **.

After the apple is peeled, the phenols in the cells will react with the oxygen in the air under the action of phenols, and a large amount of quinones will be generated.

The new quinones can cause the cells to turn brown rapidly, a change called enzymatic browning of food.

Apples turn yellow after peeling them for a while.

This is also the case with apples and pears and some vegetables.

If the apple is left for a long time after peeling, and the oxidative decomposition of the cells in the air is intensified, then the nutrients in the outer layer of the apple are decomposed more, and the pectin substances are further decomposed into pectic acid and methanol under the action of enzymes.

It makes the flesh loose, moist, discolored, tasteless, and even rotten. Wish.

The apple is all open, and it will turn yellow after a while, teaching you a trick to effectively prevent the flesh from changing color.

That's oxidized. If you soak the cut apples in lightly salted water for a while and then take them out, they won't turn yellow in a short time! Pears can be treated like this!

Because apples turn yellow when they are opened, they turn yellow.