That's very interesting, as while I have a good sanitary regime when making beer, there's not much you can do with apples apart from wash the mud off with a garden hose and send them to the scratter and ultimately the press. I, too, have never had a batch of cider go off. I wonder what the big cider-makers do. Not much more, I think. I once tried pasteurising a batch of juice- the cider tasted like stewed apples.