How To Stop An Avocado From Turning Brown I love Avocados, but as soon as I cut one open the first question would of course be “how to stop an avocado from turning brown” I can never eat a whole avocado quick enough then it tuns a gross slimy brown, right? I have used lemon juice to keep the avocado from turning brown super quick, if I plan on using it in a salad later that day.