I'm going to disagree with Brad, there is no reason you could'nt collect wort, freeze and then boil when ready to use. I'm no lab guy, but how would that be any different from making beer in the first place, besides the freezing step? We collect wort, boil, cool and pitch yeast. We then have beer. Doesn't really matter if it was frozen before it was boiled, as long as it stays frozen and does get boiled before yeast is introduced.