Canned goods

• Canned goods are one of the most common sources of damaged and potentially dangerous foods around. Always check cans before purchasing, and also before cooking. If the cans are dented, bulging or rusty, discard the can and contents immediately. Any sign of damage like this can be an indication that organisms are growing in your food, and heat will not destroy most of them. Simply throw them away.
  
  

Dry packaged food

• Most dry goods are safe even if the box or packaging has been dented. Check to make sure that the package hasn't been torn, however. If it looks like part of the box may be torn, inspect the package to see if any foreign object may have gotten inside with the food. Insects, pieces of metal or other dangerous objects may easily get mixed in with dry goods through open packaging. Don't purchase any package that appears to have been totally opened at any point.
  
  

Refrigerated food

• Check the thermometer in your grocery store's refrigerated section. They must have one visible, but it may be difficult to find. The temperature should read between 33 and 38 degrees. If the temperature is not within this range, the food here is a potential food poisoning hazard. Do not buy any refrigerated food that has been stored outside of this temperature range, as organisms can grow very quickly in warmer temperatures.
  
  

Frozen food

• Check the thermometer in your grocery's frozen food freezer. The temperature should be close to zero degrees. If the temperature is above 30 degrees, don't purchase anything from this freezer. Check the package itself for ice crystals growing on the outside of the box. This is a sign that the food has been thawed and then refrozen, which will negatively affect the food quality and be a possible source for food poisoning.