How to prevent fruits and vegetables from turning brown in colour after cutting?

Some fruits (pears, bananas, peaches, apple),and vegetables(potatoes) turn brown in colour after cutting because there is a enzyme called poly phenol oxidase or tyrosinase present in the cells ,after cutting when these iron containing phenol comes in contact of air it produce a set of reactions You see the browning when the fruit is cut or bruised because these actions damage the cells in the fruit, allowing oxygen in the air to react with the enzyme and other chemicals, called enzymatic browning.
How to prevent:
 When you cut fruits like banana, pear ,and apples that you don't want to turn brown ,just squeeze some lemon juice over them.No need to measure a certain amount,you can use fresh or bottled lemon juice .Now cover the fruits tightly with plastic wrap.

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