Avocados have a creamy, luxurious texture that literally melts in the mouth and a brilliant green flesh that tantalizes the eyes. But once cut open and exposed to the air, the process of oxidation turns the lovely green flesh an unappetizing brown. The acid in vinegar can slow down the browning, but it won't stop it.
Slowing Down the Brown
Acidic vinegar will slow the browning that avocados undergo when exposed to the air, giving you some time before the appearance becomes unappetizing. Typically, lemon or lime juice is used, but vinegar has the same effect. Avoid adding too much as the acidity can overpower the flavor of the avocado. The only way to truly avoid browning is to prevent contact with oxygen. If you're hoping to preserve an avocado half, put it face down on an oiled plate or completely submerge it in water. If you're hoping to preserve a prepared avocado dish, like guacamole, tightly seal it with plastic wrap, applying the wrap directly to the surface to minimize the amount of air it is exposed to.