What's new

When life gives you lemons…

By David, 18 January 2016 Activity

Several squeezed lemonsand some lemon juice

Squeeze the lemons into a bowl

Safety: This activity requires boiling water. Younger scientists should get an adult to help.

You will need

  • 2 teaspoons citric acid
  • 2 teaspoons table salt
  • 2 cups sugar
  • 1L water
  • Juice and rind of 3 large lemons
  • Kettle
  • Large bowl
  • Sieve or strainer
  • Wooden spoon
  • 2L jug/bottle

What to do

Someone is pouring sugar into the bowl.

Add some sugar.

  1. Fill a kettle with 1L of water and bring to the boil.
  2. Place all of the ingredients into a large bowl and pour in the boiled water.
  3. Stir the ingredients with a wooden spoon until the sugar has completely dissolved.
  4. Allow the mixture to sit overnight.
  5. Pour the mixture through a sieve or strainer into a jug.
  6. To drink it, add one part of the mixture to three parts cold water.
  7. Add ice and serve chilled on a hot summer’s day.

What’s happening?

 a large measuring cup full of lemonade.

Enjoy with ice on a hot day.

Few people enjoy popping a slice of lemon in their mouth, let alone sucking on tartaric acid. We’ve evolved to sense acids through the unpleasant taste of sourness, possibly to prevent us from eating large amounts of unripe fruit.

In the past, tastes have been associated with particular areas of the tongue, as a ‘taste map’. However this is a myth – while some areas of the tongue might be better at detecting certain chemicals due to the tongue’s shape and position in the mouth, taste depends on how chemicals interact with different types of cell that make up the taste buds scattered all over your tongue’s surface.

For example, acids are chemicals that release protons (or hydrogen ions). These particles cross the membrane of one type of cell and kick off a chemical chain reaction inside, causing a nerve to send a particular message to the brain.

Sweet tastes are caused by chemicals (such as simple sugars) being detected by a type of receptor that sends another signal to the brain.

It’s the brain that interprets all of the taste signals to form flavour. The mix of signals from the sweet and acidic ingredients in this recipe means you don’t notice the sourness so much, making lemonade and lemon cordial refreshing, thirst-quenching beverages rather than something that makes your mouth pucker.

Applications

On a trip to explore the wilds of western Africa in 1725, the French explorer Reynaud des Marchais documented a variety of fruits. Among them was the berry Synsepalum dulcificum, which has rather a peculiar effect when you eat it – it makes sour foods taste remarkably delicious.

The special chemical in this fruit is called ‘miraculin’. This molecule sticks to the receptors inside taste buds that are responsible for sweet flavours, making them send signals to the brain in response to any acids in the mouth. Although sour foods might taste nicer, miraculin doesn’t change the acids in them, making for a big belly ache if you eat too many sweet, sweet lemons.

More information

Science Daily: How People Perceive Sour Flavors

This article first appeared in Science by Email. Sign up to Science by Email to receive science news, activities and quizzes. It’s free!

1 comments

  1. That’s so cool that you can eat lemons after the special chemical and then it tastes sweet!!🍋🍋😅

      Reply

Leave a Reply

By posting a comment you are agreeing to the Double Helix commenting guidelines.

This site uses Akismet to reduce spam. Learn how your comment data is processed.