Question

what to be done to prevent browning of apple

Answer 1

you can prevent by sprinkling salt over the apple.

Answer 2

Here are a few ways to prevent apples from browning :
1) Put the sliced apples in water.
2) Soak it in any critic acid which is the best, and you can use lemon juice too.
3) Soak it in salt water.
4) And simple way, just refrigerate it. But I don't know to how much extent will this work out.
And all these we do to cut the contact of O2 which causes browning.
Hope dis helps you