Oxidasic casse : we also call it brown breakage. It is mainly an accident of moût, even thoughf it may arise with wines. It is the extreme oxydation, generally enzymatic (laccase, tyrosinase) polyphenols are transformed into quinones, and then in melanin . To prevent oxydasique breakage, rotten grapes shall not be harvested  (rich in laccase - hard to get rid of )  to protect moûts (and wines) against oxidation.