Orange juice has a pH level of 3. According to the pH scale, which measures acidity and alkalinity, anything less than 7 is acidic. Orange juice is acidic because it contains elevated concentrations of citric acid, which is a naturally forming preservative found in all citrus fruits.
Freshly squeezed orange juice contains approximately 9 grams of citric acid per liter, while commercially processed orange juice contains 17 grams per liter. Freshly squeezed orange juice is also high in Vitamin C and minerals such as potassium, thiamine and folic acid. Consuming acidic foods such as orange juice on a regular basis can aggravate gastrointestinal illnesses, including ulcers and Crohn's disease. The acid in orange juice can also damage tooth enamel over time.