To prevent avocado from browning in the salad, you can take a few steps. First, wait until just before serving to cut and add the avocado to the salad. The exposure to air accelerates the browning process, so minimizing the time between cutting and consumption helps. Secondly, you can squeeze some lemon or lime juice over the avocado pieces. The citric acid in the juice slows down the oxidation process, keeping the avocado fresher for longer.