Why do pears turn black when cooked?

When cooked, pears turn black due to oxidation. Put some rock sugar when cooking, sugar will enter the cells of pear, which can prevent delayed oxidation. The method is as follows:

Materials: 1 Sydney, 6 grams of rock sugar, 30 grams of water and 3 grams of medlar.

1. Material preparation: Sydney 1 piece, 6 grams of rock sugar and 3 grams of medlar.

Second, use a knife to remove the top of Sydney about 1/5.

Third, dig the pear core with a small spoon, clean the Sydney and add rock sugar.

Fourth, the pear heart is filled with cold water.

5. Cover the Sydney lid and steam on the drawer for 1 to 1.5 hours.

6. Turn off the fire and open the lid to eat.