Why does the pinch fruit change color after being bitten for a period of time?

There are phenolic compounds such as polyphenols, catechols, etc. in apples. Phenolic compounds are susceptible to oxidation to quinones (discoloration), and oxidation reactions occur due to contact with oxygen in the air and the release of phenol oxidase in cells.

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.

A drop of lemon juice on the damaged part of the apple will not only not change the color, but also retain the original flavor.

The question of the creature comes to be asked here.

Tell you that it is the role of external microorganisms, and think about it yourself.

The cause of discoloration: apples contain an oxidase, when the apple peels off the skin, the air meets the pulp, and the organic matter in the pulp is oxidized and discolored under the catalysis of oxygen enzymes, and the apple becomes an unsightly black-brown.

It can also be said that when the apple is peeled or cut and left for a while, the color of the incision surface will change from light to dark, and finally to dark brown. This is true not only for apples, but also for potato tubers, peaches, eggplants, etc., which also change color when they are cut. What's going on?

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.

The iron bivalent example in apples is oxidized by oxygen and produces trivalent ions, which are red in color.

It's oxidized, but I've heard that eating oxidized apples is also beneficial.

Because of course, the part of the apple that has been bitten will oxidize when it comes into contact with the air! So it will get dark!

This is mainly due to the discoloration reaction of phenolic-like compounds in the plant. After the phenolic compounds come into contact with the air, they are oxidized by the oxygen in the air to form quinones, that is, the discoloration reaction turns yellow, and the color changes from light to dark with the increase of the amount of reaction, and finally turns dark brown. This oxidation reaction is the result of the release of phenol oxidase in the cell after contact with oxygen.

Phenol oxidase is present in the organelles until the plant tissue is damaged, and oxygen from the air cannot enter, so no oxidative discoloration reaction occurs. When the bacterial tissue is damaged, the phenol oxidase is released and comes into contact with oxygen, and the discoloration reaction occurs. Phenolic compounds include polyphenols, catechols, etc.

Among them, polyphenols can be directly oxidized to form quinones; Catechols, on the other hand, polymerize under the action of phenol oxidase to form catechol polymers, which are dark purple, so the more polymers, the darker the section color. This is true not only for apples, but also for peaches, eggplants, potatoes, etc., which also change color when they are cut. When the fruit changes color, the vitamin content will be reduced, and the nutritional value will be affected.

If you don't eat it in time after cutting, you can soak it in salted water to prevent discoloration, so that it won't change color.

The ferrous ions in apples are quickly oxidized by the air to iron ions, which are darker in color and tan in color.

Apples contain iron, and when exposed to air, the iron oxidizes and rusts.

After the apple is plucked from the tree, it has been separated from its mother, but its breathing activity is still active. This is due to the presence of phenolic substances in apples, which maintain their respiration. When apples are peeled, the phenols in plant cells are oxidized with the air under the action of phenols, producing a large amount of quinones.

The new quinones can cause plant cells to turn brown rapidly, a change called enzymatic browning of food. So apples will change color after peeling and leaving them 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 pectin acid and methanol under the action of enzymes, making the flesh loose, moist, discolored, tasteless, and even rotten and deteriorated.

So, it is best to eat the fruit immediately after peeling. An easy way to control the discoloration of apples when giving apples to babies is to immediately soak the peeled apples in cold boiled water, sugar water, or light salt water to isolate them from the air to prevent the oxidation of phenols in plant cells. However, from the point of view of preserving the nutrients in apples, peeled apples should not be soaked for too long.

It's because the part that was bitten had a chemical reaction that met the oxygen in the air.

It is supposed to be an apple coated with wax, and after biting, the wax on the edge touches the flesh, so it isolates some oxygen. Fun life topics, come to the same talk and be criticized.

Because the apples have been left for a long time, the air is not good, so the apples are dark.

The nutrients in apples are nourished, and the oxidized apples are inedible and harmful to the human body.

Peeled apples turn black as a result of the oxidation of their nutrients Apples are oxidized and try not to eat them, and the same goes for leftovers, they are left for a long time, or don't eat them overnight, nitrite (preservative) will be produced overnight, nitrite is converted into nitrosamine in the intestines, it is a carcinogen! I hope you all have a healthy body!

Remember to adopt it.

This is mainly due to the browning of the apples by enzymes, which causes them to darken in color. There are three main conditions for the occurrence of browning: polyphenol substances, polyphenol oxidase, and oxygen.

After peeling, apples are exposed to air, and the polyphenols in them react with oxygen to form o-quinones, which are further oxidized and polymerized to form brown pigments and melanin.

Another is that the tannins and anthocyanins contained in apples are also a cause of discoloration. Different types of tannins take on different colors when they meet ferric iron. Available in greenish-black and blue-black.

Since the flesh of the apple contains a large amount of ferrous ions, after the apple is bitten, the surface is exposed to the air, and the ferrous ions will be oxidized by the oxygen in the air and turn into iron ions, which are yellow, so it looks like the apple will change color.