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How Warm is Just Sweet Enough?


Key Concepts
Taste buds, taste, smell, food science
Sabine De Brabandere, PhD, Science Buddies


Can you recall how a piece of warm apple pie or a cup of hot chocolate milk tastes when you let it cool? Maybe you even prefer to have these treats at room temperature. Why is this? Can flavor change even when you are not adding ingredients, cook or bake it? Try this activity and discover how temperature influences flavor!

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.


Our experience with flavor starts in our mouths, where the particles in food that are responsible for taste activate taste receptors called taste buds. When these taste buds are triggered, they send a signal to our brain and we perceive a particular flavor. Humans have thousands of taste buds; they are mainly located on the tip and upper parts of the tongue. They help to distinguish at least five basic tastes – sweet, salty, savory (umami), bitter, and sour – and provide information on the intensity of each of these.

Our experience with flavor does not end in the mouths; it is also affected by our sense of smell. Food releases smell-inducing particles. When these particles float into our nose, they activate our smell receptors. These receptors send a signal to our brain and we perceive a particular smell. Humans have several million specialized smell receptors; they are mainly located in our nasal cavity. When food is heated, it releases a burst of smell-inducing particles. That is why you can easily smell the delicious pie baking in the oven or a hearty soup cooking on the stove.

Our brain combines the signals from our taste buds with those received from our smell receptors to produce the broad sensation of flavor that we are familiar with. Scientists are studying the details of these processes, hoping to find ways to guide us to a healthier diet. They have found that taste buds work more efficiently at warmer temperatures compared to colder ones. Does that make us perceive the flavor of warm food more intensely? Try this activity to find out!


  • Ice cream
  • Two small bowls
  • Spoon
  • Two pieces of milk chocolate
  • Freezer
  • Volunteers
  • Water to rinse your mouth between tastings
  • Sugary soft drink or lemonade and ice cubes (optional)
  • Milk or chocolate milk (optional)
  • Coffee or a bitter-tasting tea (optional)
  • Microwave or stovetop to heat up the milk, coffee, or tea (optional)


Do the following at least half an hour before you start the activity:
  1. Place one piece of milk chocolate in the freezer. Leave the other piece out at room temperature.
  2. Scoop some ice cream in a bowl and leave it out at room temperature.
  3. Do not consume sugary or strongly flavored food shortly before you start the activity.


  1. Take the piece of chocolate from the freezer. Break off a small piece and leave the rest in the freezer.
  2. Place the small ice-cold piece on your tongue. Close your mouth and concentrate on the flavor. What does the chocolate taste like?
  3. Let the chocolate melt in your mouth. Does the flavor change as the chocolate melts? When is the flavor of chocolate the strongest?
  4. Rinse your mouth with water.
  5. Break off a small piece of the room-temperature chocolate and repeat the previous three steps with this piece. Is the initial flavor of this chocolate stronger compared to the initial taste of the ice-cold chocolate? Does the flavor change as this piece melts?
  6. Scent influences our experience of flavor. Take some more ice-cold chocolate from the freezer and compare the smell of the ice-cold chocolate to that of the room-temperature chocolate. Does one smell more strongly than the other? Could the difference in smell account for the difference in flavor?
  7. Take the ice cream from the freezer and scoop some into a bowl.
  8. Compare the smell of the frozen ice cream to that of the melted ice cream in the bowl. Which ice cream produces the strongest smell? Is there a perceivable difference?
  9. Place a spoonful of frozen ice cream in your mouth. Close your mouth and concentrate on the flavor. What is the flavor like? Is it too sweet, just right, or not sweet enough?
  10. Let the ice cream melt in your mouth. Does the flavor change as the ice cream melts? At what point do you experience the strongest flavor?
  11. Rinse your mouth with water.
  12. Taste the melted ice cream that you left out at room temperature. How is the flavor different from that of the frozen ice cream? Does it taste just as good? Why or why not?
  13. Ask some volunteers to perform the same tests that you just did. Do they experience the same changes in flavor that you did? Why do you think this happens?
Extra: Taste some more of the melted ice cream, even if you think it is too sweet. Then, without rinsing your mouth, taste the frozen ice cream again. Does the frozen ice cream taste as sweet as it did the first time you tasted it? Did eating something very sweet first change your perception of the next item you ate?
Extra: Repeat the test with a sugary soft drink or lemonade. Place one cup out at room temperature, place another cup in the refrigerator, and cool a third cup by placing it in an ice-bath in the refrigerator to make it ice-cold. Which sample do you think will taste the sweetest?
Extra: This activity compared ice-cold food with room-temperature food. Compare room-temperature with warm milk or warm chocolate milk. Be careful not to consume scorching-hot drinks! Is the smell of one stronger than that of the other? Does one taste sweeter than the other?
Extra: This activity tests sweet food. Test if the same conclusions are valid for bitter (e.g. coffee) or sour foods.

Observations and Results

Did you notice that the flavor of food changes as it undergoes a change in temperature?

Our sense of taste is more sensitive to warm food than cold food. That is why the frozen ice cream probably tasted just sweet enough, while the melted version probably tasted much too sweet. Similarly, the frozen chocolate probably had very little taste until it warmed up in your mouth. The intensity of the taste increased as the food warmed up. The smell might have become stronger, but probably not drastically. If you tried the experiment with food that had been heated, such as warm milk, you probably noticed that the intensity of the smell increased along with the intensity of the flavor.

Foods are prepared to be eaten at a certain temperature. When cooks prepare meals, they ensure that the food will be served at temperate that gives the desired flavor. However, in addition to flavor, cooks also need to think about the texture of food. If the flavor of your pizza is too strong, or you want your ice-cream to taste a little sweeter, cooling it or heating it might not be the best solution.

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Additional Resources

Why Does Food Taste Different When It’s Cold Vs. When It’s Hot?, by J. Staughton

Bake your Ice-Cream, from Science buddies

Measure Your Taste Threshold

The Nose Knows Smell but How About Taste?

Battle of the Senses: Taste Versus Smell

Science Activities for All Ages!, from Science Buddies

Free science fair projects.