Freshly pressed fruits - what's up with the nutritional content?

I've been thinking about this for a while. When the oranges are pressed, is it true that the nutritional content, like vitamin c, rapidly gets lost or is this just a myth?
If it is true, would freezing help stop this process and preserve the nutritions or are all those 100% freshly pressed juices you can buy in the store, nothing more then orange taste and sugars, with a lot less content then the beginning?

I know that many brands uses frozen pasteurized concentrates instead of non-pasteurized fruit juice, but I would like to know the truth in both cases.

It's mainly about the enzymes degrading. Enzymes are kinda like the sparkplugs of life. That's why folks who eat a lot of raw foods feel vibrant, etc. That's the hook. You end up with more metabolic enzymes as a result, as well.

Flash freeze drying is an effective way to preserve enzymes. That's how The Ultimate Meal, which i have been touting, is prepared. I imagine it is a craft in itself to to this effectively and can't say I know much about it.

Some vitamins may degrade from heat I think, but I'm pretty sure it has more to do with assimilation. The body can easily absorb all of the vitamins when the food is left whole and unadultered with enzymes intact.

So what you essentially saying is that wall mart juices *can* be healthy and nutritious?