How is it that yams turn black? Can you eat them when they turn black
4hw.org: yams have high nutritional value and good taste. Men, women, old and young like to eat them. It's very good for the body to eat yams in autumn and winter. Everyone has such experience. The yams bought home will turn black in a few days. How can yams turn black? Can the yams turn black?
What's going on when yams turn black
1. It is oxidized in the air for a long time
Chinese yam contains a certain amount of polyphenols and polyphenol oxidase. After being cut, it will contact with oxygen in the air. The activity of enzyme will increase, which will oxidize polyphenols into quinones, so it is easy to appear black. This is the same reason with the discoloration of apple, eggplant and potato after being cut for a long time.
2. It is caused by frying in an iron pot
People who often eat yam should know that yam and lotus root belong to calcium starch food. This kind of food is not suitable for cooking in an iron pot, and the phenolic substances in yam will react with iron ions to form a dark blue or black complex, resulting in the phenomenon of yam turning black.
Can I still eat yams when they turn black
No matter the phenolic substances in yams are quinones formed by oxidation or complexes formed by reaction with iron ions, they are not toxic, and both of them can be digested, which can rest assured of food and is harmless to the body.
However, the yam that turns black when it's eaten will not look very beautiful. Ordinary people have no appetite, so it's very important to learn how to make yam without turning black.
How to make yam without changing black
1. Soak with water after cutting
Chinese yam should be soaked in water as soon as possible after peeling or cutting.
2. Soak vinegar and salt after peeling
In addition to soaking in water, it is better to add a certain amount of vinegar, salt, etc. to the water after peeling or cutting, which can more effectively avoid the oxidation and blackening of yams.
3. Cooking yam in casserole
The best way to cook yam is to use a casserole. When cooking in an iron pot, some iron ions will dissolve in the soup, react with the phenolic substances in yam, and turn black. The casserole can completely avoid this phenomenon.
4. Blanch boiled water after cutting
The phenoloxidase contained in yam has certain activity. Therefore, the cut yam is blanched with boiling water to inactivate the enzyme on its surface and avoid blackening.
5. Quick peeling
There are a lot of whiskers on the peeled yam. When peeling, these whiskers will slow down the peeling speed. First, set the yam on fire and burn the whiskers on it quickly. In this way, the peeling will be faster and the contact time with the air will be reduced.
6. No knife cutting
If the yam touches the metal blade, it will change color. Use a bamboo knife or plastic blade to cut it, or use a spoon to make a circle on the surface of the yam, and then use a wrench to break it.
7. Heat before peeling
In order to avoid the discoloration of yam after contacting the iron pot, put the yam with skin into the steamer or microwave oven for one minute to heat, which can make the polyphenol oxidase fail, so that it will not turn black.