The main acid of citrus fruits is citric acid, which is found mainly in the fruit juice, while malate, malonate and oxalate are found mostly in the cortex. The juice of oranges usually contains 1-1.3% citric acid, however this amount can vary from 0.5 to 1.3%. The acid with the second largest concentration in citrus juice is malic acid. In oranges, the concentration ranges from 1,4 to 1,8 mg/ml of juice.
A whole orange contains on average only 85 calories and has no fat, cholesterol or sodium. On the other hand, orange is an excellent source of vitamin C, vitamin A, flavonoid antioxidants, B-complex vitamins and minerals like potassium and calcium.