Question

why we must do the acid content analysis on fruits? what is the significant of it?

Answer 1

Fruits are full of sugar molecules and sugars ferment. Acid is a byproduct of fermentation, so by testing the fruit for acid content we can see how much of the sugar inside the fruit as fermented and how much hasn't.

A case in point are bears who gorge on apples. The apples will ferment inside their stomachs. One of the other byproducts of fermentation is ethanol - drinking alcohol - so after their meal the bears go to sleep sober and wake up drunk.