When cut fruit is exposed to oxygen, a process known as oxidization occurs, causing the fruit to turn brown. While the browning does not affect the fruit's flavor, it does make it appear less appetizing. Lemon juice contains high amounts of citric acid, which will protect cut fruit from oxidization. Additionally, the pungent flavor of lemon juice can enhance and amplify the taste of fruit. Use lemon juice in fruit salad to keep its ingredients appearing fresh for up to three days.
Measure the amount of fruit salad you need to preserve. Use a measuring cup, as you need an accurate amount to prevent using too much, or too little, lemon juice.
Combine 1 tsp. of sugar and 2 tbsp. of lemon juice for every 4 cups of fruit salad. Whisk the sugar and lemon juice in a small bowl until the sugar dissolves.
Drizzle the sugar and lemon juice mixture over the fruit salad. Toss the salad with a wooden spoon to coat all ingredients with the juice.
Cover the salad with plastic wrap, and store it in the refrigerator. The lemon juice mixture will prevent the salad's ingredients from turning brown as it sets.