Why do lemons and oranges taste sour?

Here's a breakdown:

* Citric acid is a natural organic acid found in citrus fruits like lemons and oranges. It's responsible for their characteristic tart flavor.

* Acids are compounds that release hydrogen ions (H+) when dissolved in water. These hydrogen ions are what stimulate the sour taste receptors on your tongue.

* The higher the concentration of citric acid in a fruit, the more sour it will taste.

So, the sour taste of lemons and oranges is a direct result of the citric acid they contain.