I think oranges do, not sure about pineapples...
Citrus acid
lemon and oranges look it up
Ascorbic acid (Vitamin c)
oranges, lemons, limes....
an acid Vinegar, lemon, and Oranges All contain acids
You can find acids in fruits, for example oranges this contains Citric acid
the most popular oranges eaten are blood oranges, many people enjoy this types of oranges more than any other types of oranges
They Are Both Examples Of The Carboxylic Family Of Acids.
Acids and suffocation are ways that oranges kill insects. Insects can be sensitive to the acidic citrus fluids within oranges. They also may be crushed by ripe oranges falling from the canopy to the ground.
Oranges are juicy because of their water content. The fruit contains liquids such as acids, which are 78 percent in overall fruit content.
acids are of types.....concentrated acids are strong.