Acids are of many types that range from the stronger corrosive acids to weaker acids that are organic and found in fruit to amino acids that are required for life. Note that DNA itself is an acid, the complete name being deoxyribonucleic acid. Therefore, in case you are worried about acids corroding away your body, be rest assured that the body’s acid requirements consist of organic and amino acids, largely.
Fruit juices contain organic acids as a consequence of the fruit they are derived from so oranges and lemons contain citric acid, grapes – tartaric acid, and ellagic acid in some berries. All these play an important role in our bodies and in the flavors of derivatives of fruit. For example, these acids are strong antioxidants. Antioxidants are molecules capable of preventing oxidization of other molecules. When molecules are oxidized, then the result is free radicals that can damage and kill cells of the body. Antioxidants combine with these free radicals thus preventing them from damaging the body. Trying to eliminate these from your diet would cause of lot of harm to your body.
The subject of fruit juice however gives rise to the debate of processed foods versus organically made juice. Organically grown fruit and vegetables are the best sources of nutrition because the growth of the plants are not modified or adapted in any way. An example of this is the use of pesticides when growing fruit trees. These tend to leach into the soil and can eventually find its way into the fruit. If not the complete pesticide, some of the heavier metals could find their way in, and this is where organically grown fruit scores over processed foods. In addition to this, the preservatives that are added to fruit juices make them last longer. Some of these preservatives may not be completely healthy to ingest and this is also one of the criticisms against processed foods. However, most preservatives are approved by authorized bodies so their damage to the body would be minimal but it would still be a strain on the liver to excrete them from the body. This debate comes down to a matter of convenience versus unnecessary chemical ingestion, ultimately a personal choice. To summarize, the acid contents of all fruit juices are not adjusted any further than their original equilibrium and there are no acidic fruits; though as a general rule, the more sour they are, the more acid they contain in their pulp.