Why is a lemon sour?

Have you ever licked a juicy slice of yellow lemon? Your eyes squeeze shut. Your lips pucker up tight. Your whole face goes scrunch!

Oranges taste sweet. Strawberries taste sweet too. But a lemon makes your mouth go zing. So why is a lemon so sour?

Let's peek inside a lemon. A grown-up cuts it in half with a knife. Look closely, and you see many tiny pockets, packed side by side.

Each little pocket holds lemon juice. Squeeze the lemon, and the juice drips out. That juice is where the sour taste hides.

Lemon juice is full of sharp, tangy stuff. You cannot see it. It mixes right into the juice, just like sugar mixes into water. That tangy stuff gives lemon juice its strong taste.

When you take a lick, the juice lands on your tongue. Your tongue has taste buds, which are tiny tasting spots tucked in its little bumps. You have lots of them, all over your tongue. What do you think your taste buds do when the tangy juice touches them?

Your taste buds feel the tangy stuff right away. They send a quick message up to your brain. Your brain reads the message in a flash. And the message is sour!

More tangy stuff makes a stronger message. A lemon has far more tangy stuff than an orange. So your taste buds shout sour very loudly. That is why your face scrunches up so much!

Taste buds. Lemon juice is full of tangy stuff, and your taste buds feel it as sour.

Next time a lemon makes your face scrunch, you will know just why.