Marco, I think it's likely the opposite to what you think. Ammonia takes time to be absorbed into the paste. That's what is softening it, though. If the outside is very soft while the inside is still hard it means that the mold on the outside is producing ammonia faster than it can be absorbed. The solution is to reduce the aging temperature (or make shorter cheeses). This slows down the growth of the mold, which reduces the amount of ammonia which gives the ammonia that's already in the cheese time to get to the center. If you find that it's literally taking too long (like you've been aging for 7 weeks and it is still hard in the center), there are a few things to do. First, make shorter cheeses. This will make it easier to get to the center in a reasonable amount of time. Second, if you have been adding extra cream, cut back a bit -- fat slows down the absorption of ammonia. Third, make sure to go 24 hours at least before salting the cheese. You need the pH to bottom out. This removes some of the buffering in the cheese and means that the pH of the cheese will rise more easily (with less ammonia).