Before peeling yam, prepare a basin of water and add a spoonful of white vinegar. Rinse with clear water immediately after peeling, then put it in water with white vinegar, soak uncut yam in vinegar water, and put the sliced yam into vinegar water immediately, so that each yam slice will not turn black.
Boil the water in the pot, add a spoonful of white vinegar, pour the yam into the pot and boil it again. Then immediately take out the yam slices and cool them in cold water, which will make the yam more brittle, remove the mucus and make it easier to fry.
The causes of yam blackening
This is the browning of peeled yam caused by enzyme, which leads to darker color. There are three main conditions for browning: polyphenol, polyphenol oxidase and oxygen. The peeled yam was exposed to the air, and the polyphenols in it reacted with oxygen to produce o-quinone, which was further oxidized and polymerized to produce brown pigment and melanin.