Citric acid and its shelf-stable salt sodium citrate are used for modifying pH of juices, for adding a tart, acid taste to juices, as preservatives, and to help keep fruit pulp from settling to the bottom of the juice container. In the European Union, citric acid and sodium citrate are labeled as E330.
Citric acid is extracted from lemons, limes, and berries, but it doesn't carry any of the taste profiles of the fruits and berries from which it is extracted. It simply tastes sour, and can release fizzy effervescence when combined with sodium bicarbonate (baking soda). There are no health reasons not to use products made with citric acid.