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Why do bananas turn black? How to prevent them from turning black

Sihaiwang: I believe that bananas are not new to us in life. Bananas are very delicious food. And the nutritional value of banana is very high. Especially for those who want to keep fit and lose weight, bananas can meet our daily needs. But I'm sure you are very confused about why bananas turn black when they are put on? How to prevent bananas from turning black? Let's take a look at it with Xiaobian~

Why does banana peel turn black?

Banana is a kind of tropical fruit. When the temperature is below 10 ℃, it is easy to suffer from cold injury. The chilling injury showed that the pericarp became dark, the pulp could not become soft after ripening, and the fruit could not mature normally. After cold storage, it is easy to damage the peel cells, promote the occurrence of enzymatic browning, and the epidermis is also easy to turn brown or even black.

Banana is a kind of fruit that is easy to turn black, especially in summer when the temperature is relatively high. When banana is placed at room temperature, first there are spots on the surface, then more and more and more half spots, and finally the whole skin will turn black. At the same time, the texture of banana is soft, very poor, and the eating quality is greatly reduced.

This is because banana peel cells are rich in phenols and polyphenoloxidase. Normally, the two substances are separated in different areas of the cell. However, when the banana epidermis is is damaged, the two substances can meet. In addition, the damaged cells are exposed to the air, so these polyphenol oxidase catalyzes the reaction of polyphenols and oxygen in the skin to produce quinones, and then the quinones can't be stopped, and a series of reactions continue to produce catechol melanin. The longer the reaction time, the darker the color, from brown to black, so the banana turns black.

It was found that the PPO activity of banana peel was stronger than that of common fruits (such as apples, pears, etc.), so the browning speed of banana peel was very fast. Not only the outer skin of banana is easy to browning, but also the pulp is very easy to browning, and the inner core of banana pulp is easier to browning than the outer layer. So the banana won the laurel of "the most prone to blackening of all fruits".

What is the effect of blackened bananas on quality?

First of all, the Black Banana cells are more damaged, vulnerable to the invasion of microorganisms, resulting in microbial spoilage; second, the Black Banana seriously affects the appearance and appetite, and the storage capacity is greatly reduced, such bananas can only be preserved for a few days at most; third, polyphenols are an important antioxidant for human body, oxidation is a very regrettable thing. Therefore, it is necessary to prevent banana from prematurely blackening, no matter in terms of preventing microbial spoilage, prolonging storage period or nutrition.

How to prevent banana from turning black?

Starting from the principle of banana blackening, the blackening can be restrained from the following aspects. First, to reduce the bumping or mechanical damage of banana skin, we can try to place the banana arch (reverse, convex upward) instead of directly flat (square, concave contact desktop) on the contact surface; second, wrap the banana with fresh-keeping film to reduce the contact with oxygen, at the same time, form a spontaneous air-conditioning environment and inhibit its aerobic respiration; in addition, appropriate temperature The temperature we can achieve in our daily life is no more than refrigerated or room temperature.

How to prevent banana from turning black?

Arch placement

Reverse placement means that the concave side is downward and the convex side is upward. Forward placement means that we often place the banana flat on the table. The biggest difference between the two methods is the contact surface between banana and desktop. It is just that the two ends of banana are in contact with the plane to reduce the damage of pressure on the banana epidermis, while the cells at the contact surface are prone to be damaged by pressure and lead to browning.

Fresh keeping film

Wrapping with plastic wrap is very beneficial for banana storage. On the one hand, the preservative film can reduce the presence of oxygen, without which the enzymatic browning reaction can not occur; on the other hand, the preservative film is wrapped to form a spontaneous atmosphere controlled microenvironment. The carbon dioxide generated by banana's self respiration increases, and the oxygen decreases, which can restrain its own aerobic respiration to a certain extent, while not causing anaerobic respiration, and can greatly extend the shelf life. However, the banana without preservative film, exposed and in the air, has both aerobic respiration and enzymatic browning, which is easy to browning and has a short storage period.

Room temperature

Banana is a kind of tropical fruit. When the temperature is below 10 ℃, it is easy to suffer from cold injury. The chilling injury showed that the pericarp became dark, the pulp could not become soft after ripening, and the fruit could not mature normally. After cold storage, it is easy to damage the peel cells, promote the occurrence of enzymatic browning, and the epidermis is also easy to turn brown or even black. In theory, the best storage temperature of banana is 12-16 ℃, but it is difficult to maintain it in life, so it can be placed at room temperature. By combining with other methods, the storage time at room temperature can meet the needs of life.

The preservation period of banana stored in this way is at least one week longer than that of banana not stored in this way under the same conditions, and there is no blackening.