Is there a "rule of thumb"to follow for pasteurizing food?

Roberto, thank you for your response, but it doesn't really answer the questions I asked. If someone has the answer, I would appreciate hearing from them.

My answer was that in general you should use the science and existing data to figure out what you need to do. The chart (and the USDA data) can help you answer your questions:
- Should certain foods be pasteurized (by which I assume you mean the bugs in it killed to a given percentage)
It depends if you're concerned about bugs, who you're feeding the food to and what the source of the food is, certain foods are more likely to have patogens than others.
- Should ground meat be pasteurized?
Same answer, ground meat's issue is that when you grind meat the surface (which is most likely to be contaminated) gets spread throughout the mass of meat, all things being equal you should be more careful with ground meat (or sear before grinding)
- Will it change the texture of the food?
Yes. Heat cooks food, time changes food, your end result will vary with heat and time.
- When do you pasteurize only the surface and when do you pasteurize the core?
What do you understand by pasteurization? I'm not sure I understand the question.

It's really quite scientific, by which I mean that it is precise and measurable.
Take a moment to understand this chart:
http://www.cookingissues.com/wp-content/uploads/2010/02/bacteria_time_temperature2.jpg

And follow the links at the bottom of the graph for detailed temperatures for various meats.

Killing of harmful microorganisms is a function of time and temperature, the higher the temperature the less time is needed to kill the bugs, different bugs survive and thrive at different temperatures as well.

Pasteurisation is the process of killing the vast majority of bacteria present, it is a form of preservation. You can't really pasteurise "just the surface", because any bacteria in the centre of your food can move to the surface afterwards.
Anyway, so long as you are cooking your food above 55 deg C ( I think that's about 130 F) you only need to pasteurise food if you are planning on keeping it unfrozen for longer than you could keep it unfrozen raw. You certainly don't need to pasteurise anything you're planning on eating immediately, no matter what it is. You also don't need to pasteurise anything you are going to freeze, freezing and pasteurisation are two different types of preservation. Freezing stops any existing bacteria from multiplying, pasteurisation reduces the number of bacteria present.
Be aware though, that pasteurisation doesn't kill ALL bacteria, and the food will go off eventually. Frozen food does not go off at all so long as it stays frozen, but the taste and texture can change over time.
I think what you're getting mixed up about is very low temperature cooking. If you cook a piece of meat at a low temperature (below 55C or so) for a very long time, you will most likely grow bugs in it. Best thing to do is cook it hotter or shorter. I wouldn't trust any "surface pasteurisation" to keep my food safe.