By America’s Test Kitchen

Does boiling green beans in salty water change the way they cook? The way they taste? This experiment gives you the answer—and a side dish to eat!

Total time: 1 hour

Materials

2 quarts plus 2 quarts water, measured separately

Large saucepan

Masking tape

Marker

Serving platter

8 ounces plus 8 ounces green beans, measured separately, ends trimmed

Large bowl

Ice

Colander

Dish towel

¼ cup table salt

1 plate per taster

1 fork per taster

Let’s Go!

1. Make a prediction. Do you think green beans cooked in salty water and green beans cooked in plain water will look the same or different? Will they taste the same or different? Why do you think so? 

2. Add 2 quarts water to large saucepan. Bring to boil over high heat.

3. While water heats, make 2 masking tape labels. Use marker to write “Salted” on 1 label and “Unsalted” on second label. Stick labels on opposite ends of serving platter. 

4. Add 8 ounces green beans to boiling water in saucepan. Return to boil and cook for 10 minutes.

5. While green beans cook, fill large bowl halfway with ice and cold water. (This is called an ice bath.) Place colander in sink. When beans are ready, carefully drain beans in colander (ask an adult for help).

6. Immediately transfer drained beans to ice bath. Let sit until no longer warm to touch, about 1 minute. Drain beans well. Transfer beans to dish towel and pat dry. Then transfer beans to side of serving platter labeled “Unsalted.”

7. Add remaining 2 quarts water to now-empty saucepan. Bring to boil over high heat. Add ¼ cup salt and remaining 8 ounces green beans to boiling water in saucepan. Bring to boil and cook for 6 minutes.

8. While salted beans cook, return colander to sink and make second ice bath in now-empty large bowl.

9. When salted green beans are ready, carefully drain beans in colander (ask an adult for help). Immediately transfer drained beans to ice bath. Let sit until no longer warm to touch, about 1 minute. Drain beans well. Transfer beans to dish towel and pat dry. Then transfer to side of serving platter labeled “Salted.”

10. Observe your results. Invite your family and friends to join you for a taste test—don’t’ tell them the difference between the green beans until after they taste! First, have everyone observe the two types of green beans. Then, have everyone taste a few of each type of bean. Have tasters keep their thoughts to themselves until everyone has observed and tasted. Ask tasters:

•How would you describe the color of each type of green bean?

•How would you describe the flavor and texture of each type of green bean?

•Do the two types of green beans taste the same or different?

Understanding Your Results

(Don’t read until you’ve completed the experiment!)

The Big Ideas

• Cooking the green beans in salty water seasons the beans inside and out thanks to a process called diffusion. 

• The longer green vegetables cook, the duller their green color becomes.

• Green beans turn tender more quickly when they’re cooked in salty water, which helps them keep their bright-green color.

Whoa! In the Recipe Lab, the green beans we cooked in salted water cooked in almost half the time–and stayed bright green!—compared to the beans we cooked in plain water. Plus, the saltwater beans tasted more seasoned and, well, green-beany. What about yours?

As vegetables cook, they become more tender and easier to chew, partly because the “glue” that holds plant cells together (called pectin) gets weaker. But something else happens as green vegetables heat up—they start to lose their bright green color. And the longer they cook, the duller and more drab their color becomes. Salt to the rescue! Adding all that salt to the cooking water is like pressing fast-forward on cooking the green beans. Salt weakens the pectin in green beans. This causes the green beans to become tender much more quickly. And less time in hot water means that these beans lose only a tiny bit of their bright green color.

Cooking green beans in salty water also seasons them, inside and out! Tiny molecules and ions, like the salt dissolved in the boiling water, naturally move from places where there are lots of them (the salty water) to places where there are few of them (the inside of a green bean). This process is called diffusion (“di-FEW-shun”). As the green beans cook in the salty water, some of the dissolved salt moves from the water into the green beans. This makes the beans taste what we call “seasoned.” (Even though you added ¼ cup of salt to the water, only a tiny amount makes its way inside the beans.) The extra bit of seasoning brings out the flavor of the green beans. Thank you, salt!  ¶

Reprinted, with permission, from The Complete Cookbook for Young Scientists by America’s Test Kitchen (2021), americastestkitchen.com.