"Derek Lyons" wrote in message
...
Another reason is that properties of foods can vary by quite a bit.
Bakers have it even worse because the enviroment in the kitchen can
further amplify these differences.

And doneness temperatures for meats can vary depending on cooking method.
Cook something for long enough and an internal temp of 145 F can be more
done than the same cut quickly cooked to 160F. One of the most reasuring
experiences of my culinary life was finding out that salmonella is killed at
137 F., at which temperature chicken is still inedible.