Lots of people think food is safe longer than it really is. Here's a breakdown of what the USDA says:
Refrigerated foods should be safe as long as the power is not out more than a few hours and the doors have been closed. The magic number is 40 degrees. Potentially hazardous foods should be discarded if they warm up above 40 degrees.
Throw out any meat, poultry or seafood products if the power has been out for more than a few hours. This goes for raw AND cooked meats. Most cheese, eggs, milk and other dairy products must also be thrown out at this time. Also discard cooked foods like beans, rice, potatoes, pasta and pasta salads. Foods that won't spoil but might lose quality are salad dressings, mayonnaise, butter and margarine, and hard cheeses.
When it comes to frozen foods, USDA says an unopened freezer should keep food safe for 2 days. Remember, frozen foods that have begun to defrost are still safe if they have ice crystals or are still cold. You can safety re-freeze these foods, however, the quality may not be as good. If your power is still out, you can re-freeze these foods with a block of dry ice in a cooler. And discard anything that reaches room temperature.
When in doubt, throw it out. You simply can't rely on appearance or odor.