Vinegar contains acetic acid, a week organic acid, produced by fermenting bacteria on apple juice. Acetic acid kills the fermentation bacteria at 5% strength. Interestingly, there is a species of microorganism that can survive 5% acetic acid called Vinegar Eels or Turbratrix aceti. https://www.youtube.com/watch?v=7Vzp3CnrBpY Vinegar will in general disinfect items of bacteria because of its acidity. The figure below the indigo glass shows an acetic acid molecule combining with a water molecule to form acetate negative ion and a positive hydronium ion or acid. Only a small percentage of molecules turn into acid ions and that is why it is a weak acid.