Yeah I know although I think that concern is vastly overblown, also the compression from a hydraulic press is going to cause some heat as well. I have measured the temperature of carrots before and after juicing and the increase is barely measurable. Try pouring water through a juicer at room temperature and see how much it increases, it on the order of 1/100th of a degree. I think that if you are talking industrial scale it might matter, but they pasteurize factory juice anyway. They enzyme destroying heat of the centrifugal juicer is a story used to sell crazy expensive juicers, like the norwalk.

That being said, I have a hydraulic press that I built instead of getting the norwalk, although I use their filter bags. The main benefit from the press is that you get all the juice there is. You can press out another half cup of juice or more from the pulp left over from a centrifugal model. The stuff truly is so dry and depleted that animals don't even eat it (maybe goats).