We’re having apple fever around here this week! But I’ve been hating how apples turn brown so quickly. Maybe not as much as my picky 3 1/2-year-old, but annoyed just the same… So we decided to test a bunch of those methods you see out there for keeping the apples looking fresh. And why not turn experimentation into a lesson? So we threw in some Scientific Method for kicks, too. Read on for a fun experiment for kids and what works best for keeping apple slices white.
This apple experiment is a great chance to teach the kiddos about the Scientific Method. Why should you bother? The method teaches kids and adults critical thinking and a framework in which to approach any problem, not just ones in science. You can follow along with the experiment and the method below. This is a great STEM activity you can do with ingredients right in your kitchen. With the kids home more these days, you’ll be glad you have this quick educational experiment you can pull out of your back pocket anytime!
Scientific Method Step 1: Ask a Question
We hate it when apples turn brown. For some reason, they just don’t seem as tasty as when you first bite into them. So our question is: What is the Best Way to Keep Apples From Turning Brown?
Scientific Method Step 2: Do Research About Why Apples Turn Brown
I thought it would help the process to first learn what makes apples turn brown in the first place. Essentially your apple is rusting in a process called oxidation. Once the apple is cut or bruised, oxygen in the air combines with iron in the apple to form iron oxides. Enzymes in the fruit (like polyphenol oxidase) make this process go faster. The oxidation process is also what causes metals to rust.
You can reduce browning by slowing oxidation in three different ways. 1) Cook the apples 2) reduce the exposure to oxygen or 3) reduce the pH of the fruit. Doing both by covering in an acidic liquid is the best way to keep apples from turning brown without cooking.
Scientific Method Step 3: Form a Hypothesis
It’s time to formulate a hypothesis… Before the experiment, ask the kids a couple of questions. Their opinions will be their hypothesis.
- Which method do you think will work the best?
- Which one do you think will taste the best?
Scientific Method Step 4: Design an Experiment
It seems like everyone has an idea of the best way to keep apples looking fresh! We asked our friends for ideas (ummm, I mean I looked on Pinterest.) Here’s what we tried… Be sure to add a control that will show you how the apple turns brown with no treatment. A control is the part of the experiment that tests what an apple would do naturally, without treatment.
- Honey (1 teaspoon honey mixed with 1 cup water)
- Lemon juice (1 teaspoon juice mixed with 1 cup water)
- Salt (1/2 teaspoon salt mixed with 1 cup water)
- Vitamin C (1 tablet crushed and dissolved in 1 cup of water)
- Lemon-lime soda
- Carbonated water (bubble water)
- Tap water
- Experiment Control (we used the apple core)
Now it’s time to try all of these ingredients.
- First set out 8 bowls big enough to cover the slice completely with the solution. Label each bowl so you don’t mix up the solutions.
- Make each of the solutions in a separate cup.
- Cut one apple into 8 slices of approximately the same size. If you use more than one apple, you’re adding variables to the experiment as some apples may brown at different rates than the others.
- Place an apple slice into each bowl. You can use the core as the control.
- Immediately cover with each solution, one per bowl.
Scientific Method Step 5: Record and Analyze Data
Now comes the waiting period. We checked after 5 minutes and decided to wait another 5 minutes before pulling the apples out of the solution. You can choose your own time period based upon how fast the apples are turning brown. Then:
- Pour off the solution and inspect each apple for brown color. Record levels.
- Taste apples and record impressions.
Our lab worksheet will make it super easy to record and analyze the data!
Scientific Method Step 6: Draw a Conclusion
To help draw a conclusion from the experiment, ask the kids:
- Which one tastes the best?
- Which ones kept the apples the whitest?
You and the kiddos should test this for yourself, but here’s what we found in the experiment:
- Plain water doesn’t work. Carbonated water is a touch better, but not that much. Plus it gives a slightly bitter taste to the apples.
- Salt keeps the apples really white, but yuck! did not taste good. Probably need to try this with less salt.
- Lemon juice works well too but also changes the flavor of the apples. Good for fruit salad, maybe not for plain apple slices.
- Vitamin C works just ok, but definitely not well enough to be worth the hassle of crushing tablets.
- The lemon lime soda worked too, but they tasted like apples soaked in soda. Duh, right? Too candy-like and not really that healthy, so out.
So the winner is…HONEY! The apples weren’t quite as white as with salt and lemon, but the taste was sooo yummy. Like unadulterated apples, just deliciously sweet ones.
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