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Many fruits like Apples, pears, peaches, plums, nectarines and others that appear bruised are most often usable. It is because the bruised portion of the fruit can be easily cut off with a small knife, and very little of the fruit is wasted. 
The bruising is most often caused by the handling and methods 
by which the fruit is shipped and reaches us.
Fruit such as oranges, lemons, limes and grapefruit may appear bad, but are perfectly fine to eat. Do not discard citrus fruit unless the skin has rotten through to the flesh, and the fruit has shriveled, your finger easily pierces the skin.
Here are some properties of the fruit and vegetable peels:
Peel is rich source of dietary fiber
Peel is low in calories, sugar and fats
The peel of some fruits contains considerable amounts of mineral and vitamins.
Certain fruit peels like in orange contain rather higher levels of vitamin C than its juice.
Peel of some of the common fruits like blueberries, grapes and guava contain higher concentration of anti-oxidants.
Cucumber peels are used in beauty care for tightening the face skin, hydrating and moisturizing effects. Potato peels can reduce puffiness around eyes.
The peels of the fruits and vegetables can be put to their best use.