Re: What kind of acids are in orange, cranberries,pineapple,and apple juice?

This answer just considers acids that are naturally present. Check labels of 
processed fruit juices to see if they contain added acids.

The predominant organic acid in oranges is citric acid with smaller amounts of 
malic acid, fumaric acid and tartaric acid. Cranberry is reported to contain 
mainly citric acid, malic acid, and quinic acid. The predominant acid in 
pineapple is malic acid with smaller amounts of citric acid. Apples contain 
large amounts of malic acid, which is also known as apple acid. Small amounts 
of a variety of other organic acids are also found in fruit juices; see the 
last reference.

The USDA National Nutrient Database cited in the references lists nutrient 
content for all sorts of foods. All the fruits listed contain small amounts of 
ascorbic acid (vitamin C) and many different amino acids and fatty acids. 

References


USDA National Nutrient Database


Frozen Concentrated Orange Juice From Florida Oranges


Main Organic Acid Distribution of Authentic Citrus Juices


Malic acid


Pineapple


Pineapple In depth nutrient analysis


Cranberry - (Vaccinium macrocarpon) Profile


Verify Fruit Juice Quality from Organic Acid Profiles


Determination of Organic Acids in Fruit Juices