What is the reason why yam turns black

Yam is a food with extremely high nutritional value. It contains rich vitamins and other substances that can supplement the human body's nutrition. Yam can not only be used in cooking, but also in making porridge. It has a soft texture and is suitable for people of all ages. It is a good choice for health-preserving diet therapy. Many people find that when cooking yam, the yam turns black after peeling it. So, what is the reason why yam turns black?

Can I eat yam if it turns black after peeling?

Yams that have changed color due to mold cannot be eaten, but yams that have changed color due to oxidation can be eaten. Fresh yams are easily oxidized by oxygen in the air and are prone to browning when in contact with metals such as iron knives, making the white yams look black. So there is no problem with the yam turning black, just eat it with confidence.

The cut yam turns black due to the enzymatic browning that causes the color to darken. There are three main conditions for the occurrence of browning: polyphenols, polyphenol oxidase and oxygen. After the yam is peeled and exposed to the air, the polyphenols in it react with oxygen to produce o-quinone, which is further oxidized and polymerized to form brown pigment and melanin.

This situation is not uncommon in real life. After peeling, apples, eggplants, lotus roots, etc. will undergo enzymatic browning, causing the color to darken. If the peeled yam is soaked in cold water to isolate it from the oxygen in the air, it will not change color. There is no problem if you eat it, but the color will not look good after the dish is cooked.

How to peel yam without turning it black?

The phenolic substances in the yam are oxidized into colored quinone substances when they come into contact with oxygen in the air. They do not need to be in direct contact with the air, such as by soaking them in water. You can use salt water. You can also put some white vinegar in a bowl of water, and the cut yam will not turn black when placed in the vinegar water.

If you don't want the yam to be oxidized, it is recommended to peel it and soak it in water. If you soak it in hot water, it can not only prevent it from being oxidized and blackened, but also neutralize the biological alkali in the yam that makes people's hands itchy, and reduce allergic reactions when scratching with your hands.

When cooking yam, you should also pay attention to some tips, because the new yam is easily oxidized by oxygen in the air, and will also change color after coming into contact with iron and other metals. Therefore, it is best to process the cut yam after some treatment. You can use a bamboo knife or plastic blade to draw lines on the skin, and then peel it into sections with your hands. You can also soak the cut yam in rice wine first, and then blow it with a hair dryer to promote the healing of the incision, then wrap it with a napkin, wrap it with several layers of newspaper, and place it in a cool corner for later use.

There is a trick to peeling yam: wear gloves and peel in water

Yam is delicious and nutritious, but it has a drawback: your hands may easily get allergic reactions if they come into contact with the mucus. This is because the mucus secreted by yam contains phytoalkaloids and saponins, which are highly irritating. It will cause itching when it comes into contact with the skin, and washing with water will not help. When peeling the yam, if it gets on your hands, you will feel uncomfortable for a while. What is the most convenient way to peel the skin?

Experts recommend wearing plastic or disposable gloves when peeling yam in water. This will not only prevent the mucus from sticking to your hands, but also prevent the yam from slipping in your hands.

What should you do if mucus accidentally gets on your hands? First wash them with clean water and a little vinegar. Yam skin can easily cause skin allergies. Do not touch the skin with your hands after peeling yam. Wash your hands several times immediately, otherwise you will scratch wherever you go and get itchy. Applying cooking oil to the hands may provide relief. After slicing the yam, it needs to be soaked in salt water immediately to prevent oxidation and blackening.