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Do You Have the Willpower to Taste Something Sour?


Key Concepts
Biology, taste, food preferences, age
Teisha Rowland, PhD, Science Buddies


Have you ever wondered if people of all ages love sour foods, or if age correlates with this preference? There are a lot of different kinds of sour candies and drinks you may have seen advertised before, some having only a mild sour flavor and others that are truly mouth-puckering! In this activity you will investigate if there is a difference between the sour preferences of kids and adults. If you developed a super-sour food, to whom would you try to sell it?
This activity is not recommended 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.


Do you know anyone who likes to eat lemons? Or loves really sour candies? Maybe you are one of those people? People have different definitions of what they find palatable, or tasty to eat. There are many different factors that go into deciding whether or not something is palatable. One of the biggest parts of that decision is how something tastes. Humans can sense five tastes: sour, salty, bitter, sweet and umami (oo-MAH-mee), which is the non-salty part of how soy sauce tastes.

Taste is detected by the taste buds that line the tongue and other parts of the mouth. Although there is some variation from person to person, the human tongue has an average of about 10,000 taste buds. Inside each taste bud are several receptor cells. These cells can sense the five different tastes and send that information to the brain. 

In addition to taste, people think about several other factors when deciding if something is acceptable to eat. These include other components of flavor, such as how spicy a food is or how it smells, the texture and temperature of a food, and whether the food is something they like eating for cultural or personal reasons.


  • Five containers (must be able to hold one liter each)
  • Citric acid, which is used for sprouting or canning foods. It can be found as a powder or granules in some grocery stores in the spices, baking supplies, or health supplements aisles. It can also be ordered online from some vitamin companies, such as LuckyVitamin.com and TheCatalog.com. Caution: Only use food-grade citric acid.
  • Water
  • Measuring spoons
  • Measuring cups
  • Masking tape
  • Permanent marker
  • Citrus-flavored powdered drink mix, such as lemonade flavor (enough to make four liters or four quarts)
  • 50 small paper cups
  • Large work surface
  • Adult volunteers (at least five)
  • Kid volunteers between the ages of five and 11 years old (at least five)


  1. Make sure the citric acid you have is food-grade citric acid.
  2. Into one of your containers, put six tablespoons (Tbsp) of citric acid and three cups of water. Mix the citric acid mixture until all of the citric acid is dissolved. 
  3. Each of the remaining four containers will hold a different lemonade batch.  Using masking tape and a permanent marker, label each of the four containers as "1," "2," "3" or "4." 
  4. Following the directions on the package of the lemonade drink mix, add enough of the drink mix powder to each labeled container to make one liter of the drink (per container). 
  5. In the container labeled "1," add four cups of water.
  6. In the container labeled "2," add four cups of water and three Tbsp of the citric acid mixture.  This is similar to 10% lemon juice in sourness.
  7. In the container labeled "3," add three and 1/3 cups of water and 2/3 cup of the citric acid mixture. This is similar to 50% lemon juice in sourness.
  8. In the container labeled "4," add two cups of water and two cups and two Tbsp of the citric acid mixture.
  9. Mix each lemonade batch until the drink mix is completely dissolved.  Refrigerate the containers until you are ready to have your volunteers taste-test them.
  10. Right before taste-testing, label 10 paper cups as "#1," 10 as "#2," 10 as "#3" and 10 as "#4."  If you have more than 10 volunteers total, you will need to label and use more cups.


  1. On a large work surface, set out all of the labeled paper cups. Pour the lemonade batches into the appropriately labeled cups. For example, batch 1 (the lemonade without any citric acid added to it) will go in the cups labeled "#1." Try to keep each batch grouped closely together.
  2. Pour plain water into 10 more cups (or more if you have more than 10 volunteers total). These cups don't have to be labeled.
  3. Give each volunteer one cup with lemonade batch 1 and ask them to try it. Then give each volunteer a cup of water and have them take a sip to clear their palettes. How do the volunteers react to drinking the lemonade?
  4. Continue passing out the lemonade, one cup and batch at a time, asking the volunteers to taste it, and always having the volunteers take a sip of water in between tastings. How do the volunteers react to drinking the different lemonade batches?
  5. Once the volunteers have tasted all four batches of lemonade, ask them which was their favorite and which was their least favorite. 
  6. Do adults and kids choose different lemonades as their favorite? Did more volunteers in one age group choose the sourest lemonade as their favorite? What about as their least favorite?
Extra: Try this activity again but use more volunteers, such as 15 adults and 15 kids. When using more volunteers, do you see a stronger taste preference trend?
Extra: In this activity you investigated preferences for the taste sour. But what kinds of preferences do people have for the other tastes (sweet, salty, bitter and umami)? Think of a way to test these other tastes and then try it out. Do kids and adults have different preferences for other tastes?
Extra: Does being a "picky" eater change how likely a person is to enjoy really sour foods? Find volunteers and ask if they're picky, normal or adventurous eaters. Try to get at least 10 people in each category. Then repeat this activity with them. Do you see any correlations between the kind of eater a person is and whether they enjoy very sour tastes?

Observations and Results

Did the kid volunteers like sourer lemonade batches most, whereas the adult volunteers did not? Did the adult volunteers prefer less sour lemonade batches?

One job food scientists can have is working at companies to help design new foods. One of the things they have to do is conduct sensory analysis, which is the scientific process of determining how people react to different foods, and then make decisions about whether or not they like them. Food scientists already know a lot about people's food preferences. For example, they know that babies usually prefer sweet foods, like applesauce and sweet potatoes, over more bitter foods, like broccoli. They also know that Americans and Europeans like mint-flavored toothpastes, while people in China and Japan prefer their toothpastes to be fruit-flavored. But what about sour flavors? There are a lot of sour candies and drinks advertised on TV, in magazines and in other places that tempt kids, but not many of those advertisements make the foods sound appealing to adults. There as a good reason for this: in general, kids really do prefer sour tastes much more than adults do. In a study similar to this activity, researchers found that over one-third of kids tested preferred the sourest food tested, whereas virtually none of the adults preferred this food.
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Additional Resources

What are Taste Buds? from KidsHealth
A Sour Taste in Your Mouth from ScienceNews for Kids
Physiology of Taste from R. Bowen of the Colorado State University
Heightened Sour Preferences During Childhood from Gjin Gie Liem and Julie A. Mennella in the journal Chemical Senses
Do You Have the Willpower to Taste Something Sour? from Science Buddies

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