Orange juice is a fruit juice obtained by squeezing, pressing or otherwise crushing the interior of an orange. The largest producer and exporter of orange juice is Brazil, with 80% of the world's production, followed by the United States.
Orange juice is an excellent source of vitamin C (ascorbic acid) and potassium. It is also an important natural source of folic acid (Vitamin B9), which is recommended for women who are pregnant or may become pregnant. Citrus juices contain flavonoids that are believed to have beneficial health effects. However, if drunk on an empty stomach, orange juice can exacerbate present gastro-intestinal conditions and/or cause mild and temporary stomach upset. Due to the citric acid, orange juice typically has a pH of 3.5. Drinking or sipping orange juice can therefore cause erosion of the tooth enamel, otherwise known as 'acid erosion'. It is recommended to use a straw so that the juice does not come into contact with the teeth. 200 ml of orange juice accounts for 1 of the recommended 5 pieces of fruit a day.
Refrigerated juice shipped in liquid form is traded between producers as direct juice. In the USA all commercial orange juice is pasteurized. Some refrigerated fresh juice is sold to consumers. In the U.S., Canada and the U.K. it is labeled "not from concentrate".
Freshly squeezed juice and filtered orange juice is pasteurized and is evaporated under vacuum and heat to remove most of the water before it is frozen. This process strips out certain essences and oils. The concentrated juice, about 65° brix, is then stored at about +10°F (-12°C). At this point essences and oils (recovered during the vacuum concentration process) are added back to restore the flavor. To make cans of frozen concentrate for sale, filtered water is added back to bring the brix level down to 42° (about 3 times more concentrated than fresh juice).
When water is added to freshly-unfrozen concentrated orange juice, it is reconstituted. Most of orange juice sold today throughout the world is reconstituted juice. There is a huge difference in the volume of frozen concentrated orange juice and unprocessed juice and this makes a difference in the price the consumer is charged. Orange juice containing pulp seems to be more nutritious than no-pulp varieties because of the flavonoids contained in the pulp.