Its the electrolyte balance that guides the pH, the ratio of cations to anions..

It will be more interesting to know why pH of most of fruis and vegetables remains acidic in nature..

Fruits are usually rich in organic acids notably malic, citric and tartric, and of course their balance with ions is what determines the pH from a physico-chemicla point of view. How this balance is controled (biologically) is another issue. Organic acid contents decrease upon maturation and storage. But not necessarily pH.

Thank you Mr Anoop Kumar Srivastava

Thank you Catherine M G C Renard

Can you explain more about the balance between acids and ions in fruits?