Although freezing food puts pathogens (disease-causing bacteria or other microorganisms) in suspended animation, it does not kill them. As soon as the food starts to become warmer at temperatures above 40°F, bacteria can begin to multiply. So, when thawing frozen food, it's important to keep it out of the "danger zone" of temperatures where bacteria thrive.
The following thawing methods are recommended by food safety advisors:
• 1. In the refrigerator: This is the easiest method but it takes a long time, so you must plan ahead. (A pound of meat can take a entire day to thaw.) Advantages to this method are that it's hands-off and the refrigerator keeps food at a safe temperature. You can thaw dinner during the day while you're at work – and if you decide to eat out instead, the food will be safe for eating later or refreezing.
• 2. In cold water: Sealed packages of food may be thawed in cold water. Place the package under water in a bowl, pot, or sink and change the water every 30 minutes until the food is defrosted.
• 3. In the microwave: Microwave thawing may be uneven, leading to poor quality or even bacterial growth. It's best to use this method if you're going to cook the food, or for frozen fruits and berries that you're going to serve immediately.
• 4. At room temperature: Pastries, breads, and fruits may be thawed for 2-4 hours at room temperature. Do not use this method for meat, fish, and vegetables.
• 5. Under running water: Meat may be thawed under cool running water. See Kitchen Shortcut: How to Thaw Meat Quickly.
More thawing tips: National Center for Home Food Preservation