Sensory Science: Testing Taste Thresholds

• Measuring spoons
• Water, preferably distilled
• 12 paper or plastic cups
• Permanent marker
• Kitchen scale or measuring spoons
• Granulated sugar, or sucrose
• Table salt
• Vinegar
• Spoons
• Cotton swabs
• Paper towels
• Piece of paper and pen or pencil (optional)
• Taste test volunteers (optional)

1. Pour six tablespoons (Tbsp.) of distilled water into a paper or plastic cup. Add 10 grams of sugar (or about 2 ½ teaspoons [tsp.]) and stir until the sugar is dissolved. This gives you an approximate 10% sugar solution. Label the cup.
2. Pour two tsp. of the 10% sugar solution into a new cup. Add six Tbsp. of water to it and stir. This gives you a 1% sugar solution. Label the cup. 
3. Repeat this dilution process (diluting two tsp. of the previous solution in a new cup with six Tbsp. of water) to make 0.1% and 0.01% sugar solutions. These are called serial dilutions. Be sure to label the two new cups. What do you think is the lowest concentration you’ll be able to taste the sugar in?
4. Repeat these steps (using clean utensils) to create salt solutions that have concentrations of 10%, 1%, 0.1% and 0.01%. Label the cups. For 10 grams of salt, you can use 1 ¾ tsp. of salt. What do you think is the lowest concentration you’ll taste the salt in?
5. Again repeat the steps (using clean utensils) to create vinegar solutions that have concentrations of 10%, 1%, 0.1% and 0.01%. Label the cups. Use two tsp. of vinegar initially. What is the lowest concentration you think you’ll taste the sour vinegar in?

1. Rinse your mouth with plain water and wipe your tongue dry with a clean paper towel. Dip a clean cotton swab into the 10% sugar solution and smear it all around your tongue. Can you taste the sweetness?
2. Repeat the previous step to test the 1%, 0.1% and 0.01% sugar solutions, rinsing your mouth and wiping your tongue before testing each solution. Which solution is the lowest concentration at which you can still taste the sweetness? This is your approximate taste threshold for sugar. You can write this down to remember later.
3. Rinse your mouth with plain water and wipe your tongue dry with a clean paper towel. Dip a clean cotton swab into the 10% salt solution and smear it all around your tongue. Can you taste the saltiness?
4. Repeat the previous step to test the 1%, 0.1%, and 0.01% salt solutions. Which solution is the lowest concentration at which you can still taste the saltiness? This is your approximate taste threshold for salt. You can write this down.
5. Rinse your mouth with plain water and wipe your tongue dry with a clean paper towel. Dip a clean cotton swab into the 10% vinegar solution and smear it all around your tongue. Can you taste the sourness? Repeat this process to test the 1%, 0.1% and 0.01% vinegar solutions. Which solution is the lowest concentration at which you can still taste the sourness? This is your approximate taste threshold for vinegar. You can write this down.
6. Were your taste thresholds (the lowest concentration at which you could still taste the flavor) the same for all three tastes, or did you have lower thresholds for some of them? Did the solutions that were 10-fold more concentrated taste 10-times stronger?  

Extra: Try repeating this activity using several volunteers. Compare your results. Do some people generally have lower thresholds than other people? Is there variation in which taste has the lowest threshold for people in the group? 

Extra: Recruit several volunteers in different age groups to take this threshold of taste test. Does taste threshold change predictably with age?

Extra: In this activity you used 10-fold serial dilutions to roughly establish your threshold of taste. Design a test to determine your threshold with higher precision. What exactly is your taste threshold for sugar, salt and vinegar?