Soupy Science: Investigate How Dried Beans Absorb Water
Have you ever had black-eyed peas for New Year’s Day? They’re often used as part of a traditional meal in the South on this day. Dried beans themselves are a major ingredient in dishes served all over the world. In their dried form, they can be stored for years and then “brought back to life” by soaking them in water. In this science activity, you will explore how the temperature of the water used to rehydrate dried black-eyed peas (which are technically beans) affects how quickly they become rehydrated and ready to chow down on!
This activity is not appropriate for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.
Beans come in dozens of shapes, sizes and colors and have been consumed throughout the world for thousands of years. They are low in fat and are good sources of protein, carbohydrates and fiber. The U.S. Department of Agriculture dietary guidelines suggest that beans, along with other foods that are low in fat, oils and sugars (including vegetables and grains) should make up the largest portion of our daily meals.
In addition to their nutritious qualities, beans are convenient because they can be dried and stored for years. Soaking the beans in water for a few hours (or less) softens the dried beans and prepares them for cooking. This rehydration process also occurs in nature. Beans are a form of seed, and they can sprout when exposed to water. Beans remain viable for long periods of time if they are kept dry, a feature that allows them to survive prolonged periods of drought in natural settings, and that allows us to store them for long periods of time prior to cooking. As beans soak in water, their volume increases. In this science activity, you’ll determine how soaking beans in hot versus cold water affects how quickly they absorb water.
Extra: Another way to measure your results in this activity is to weigh the black-eyed peas. You could use multiple cups and weigh the beans from those cups (after straining out the water) as they are soaked in water for different amounts of time. How does the mass of the black-eyed peas change over time?
Extra: Try this activity using some different legumes (legumes include beans, peas and lentils). Do some legumes absorb water faster than others? What does this tell you about how long they might need to be soaked before cooking them?
Observations and Results
Did you find that the black-eyed peas had a higher level in the cup with the hot water over time compared to in the cup with the ice cold water?
When dried beans are soaked in water, their volume increases as they absorb the water. Beans absorb hot water more quickly than cold water, which is why the black-eyed peas used in this activity should have swelled faster in the hot water than in the cold water. For example, after only 10 minutes of soaking, you may have seen that the level of the black-eyed peas in the hot water cup was about half an inch higher than the level in the cold water cup, and that this difference remained consistent for the rest of the activity. This activity works well for dried black-eyed peas, split peas and lentils because they do not require extensive soaking before cooking; if you were to test other legumes that require more soaking, you would see that they absorb water much more slowly.
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Teisha Rowland, PhD, Science Buddies
Science Buddies |
Water, absorption, seeds
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