Citric acid occurs in orange juice in levels between 9.1 grams per liter and 16.9 grams per liter, depending on whether the juice is fresh-squeezed or commercially processed. Orange juice is a natural source of citric acid.
A study conducted in 2009 examined nutritional therapy for calcium urolithiasis and hypocitraturia by using ion chromatography to determine the levels of citric acid in a variety of citrus-based beverages. The study concluded that fresh-squeezed orange juice contains 9.1 grams per liter of citric acid and that Tropicana processed orange juice contains 16.9 grams per liter of citric acid. Lemon juice and grapefruit juice also contain citric acid.