The temperature danger zone, is the range of temperatures which are found to be the most favorable for foodborne illness causing bacteria to grow.
The standard temperature danger zone, as defined by the FDA, is from 41 degrees to 135 degrees. It must be noted that different states have different requirements for the temperature danger zone. (Some states have the low portion at 40 degrees, and some states have the high portion at 140 degrees. These distinctions are mainly for commercial food establishments, and I am providing them here for informational purposes only. When in doubt, it is better to go for the most restrictive to keep you from being in violation of your local laws.)
When working with food items, it is best to minimize the amount of time that the foods are within the temperature danger zone. In food service, the MAXIMUM amount of time an item may be in the temperature danger zone is for four (4) hours. It must be noted that this time is cumulative, so if you buy the item at the store, and it sits in the trunk of your car for an hour before you get home, that is one hour in the temperature danger zone that you have already used. If you then decide to separate it into smaller items, the time that you work on it will also add to the time it is in the temperature danger zone. If possible, you should have in your car, a cooler of some type that will help keep cold items out of the temperature danger zone.
Suffice to say, the better you are at being able to regulate the time an item is in the temperature danger zone, the better you will be at keeping foodborne illness causing bacteria from growing on your food items.