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Sonoma Family Life Magazine

Conduct an Edible Science Experiment

By America’s Test Kitchen

Sometimes you need only part of an avocado for your taco or toast. But if you save the rest for later, your avocado will turn brown (oh no!). Can you keep it fresh and green? Find out in this easy experiment. If you don’t have a whole lemon, use three tablespoons of bottled lemon juice.

Total Time 5 minutes, plus 8–24 hours waiting time

1 lemon
1 cup water
1 ripe avocado
Chef’s knife
Cutting board
Small bowl
Small plate

Get Started!
1 Use chef’s knife to cut lemon in half crosswise (not through ends). Rinse and dry knife.

2 Squeeze juice from lemon halves into small bowl. Add water to bowl.

3 Use knife to cut avocado in half lengthwise around pit. Using your hands, twist both halves in opposite directions to separate. Use soupspoon to scoop out pit. Discard pit.

4 Place 1 avocado half, cut side down, in bowl with lemon juice mixture. Place second avocado half on small plate, cut side up. Set bowl and plate in a spot where they won’t be disturbed.

5 Make a prediction: What do you think each avocado half will look like after 8 hours? Will they look the same? Different? How so?

6 Let avocado halves sit for at least 8 hours and up to 24 hours.

7 Observe your results: Turn over avocado half in lemon juice mixture. Observe the 2 avocado halves. Do they look the same? Different? What do you notice about them?

8 Eat your experiment: Both avocado halves are safe to eat—use a spoon to gently scrape off any brown parts (the flesh underneath should be green). Will you use the avocado to make guacamole or avocado toast? Will you cut it up and use it on tacos or salad?

Understanding Your Results

Don’t read until you’ve finished the experiment!

When you cut open an avocado, air touches the green flesh inside. After a few hours, the green avocado starts to turn brown—yuck!

Why does this happen? It comes down to chemistry: Molecules inside the avocado flesh react with oxygen in the air. That reaction, called oxidation (“ox-ih-DAY-shun”), creates new brown-colored molecules.

How can you stop cut avocados from turning brown? Acid to the rescue! Acids are found in ingredients such as lemon juice, lime juice, and vinegar. They are a kind of molecule called an antioxidant (“ann-tee-OX-ih-dent”). “Anti” means “against” and “oxi” means “oxygen,” so antioxidants are molecules that help prevent the oxidation reaction that turns avocados brown.

Keeping the avocado flesh under water also helps prevent too much oxygen from touching it. That’s why this combination of water and lemon juice works so well to keep the avocado green.

Reprinted from Kitchen Explorers: 60+ Recipes, Experiments, and Games for Young Chefs (2020), with permission from America’s Test Kitchen,