Fresh cauliflower has a mild, slightly sweet scent. If cauliflower has gone bad, it often gives off a strong, unpleasant smell that's hard to miss. It may be pungent, sour, or somewhat similar to ammonia or rotten eggs. This is due to bacteria and other microorganisms breaking down the cauliflower. If you detect this sort of odour, it's best to discard the cauliflower to avoid potential foodborne illness.