While topping yesterday I noticed a smell from one of the bungs that I had noticed the last time I topped. The wine inside smells fine when in a glass. The bung and bunghole, however, smell not quite like vinegar but still sort of sour, sort of yeasty like bread dough. A couple weeks ago when I first noticed it I just rinsed off the bung and wiped the hole but I would feel better if there were a way to actually fully clean it. The problem being the risk of contaminating the wine. Is there a way to clean the bunghole without jeopardizing the wine? Im assuming peroxycarb and citric are out of the question.