Here's why:

* Citric Acid: Orange juice contains a significant amount of citric acid, which gives it its tart flavor.

* pH Scale: The pH scale measures acidity and alkalinity. A pH of 7 is neutral, while values below 7 are acidic and above 7 are alkaline (basic). Orange juice typically has a pH around 3.5, making it distinctly acidic.

Let me know if you have any other questions!