Grapes should be washed, but only just before they are served or eaten. The pressure grapes put on each other when in bunches can cause bruising which creates moisture, encouraging the fruit to spoil. If they are washed before storing, water is likely to remain between the grapes and can accelerate rotting which will create soft spots.
It is best to buy grapes in small quantities, checking to make sure they are not bruised. Store them, unwashed, in a colander in the refrigerator, which allows the air to circulate and keeps them dry. Use within two to three days.
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