Why wouldn’t your blood and other fluids become significantly acidic after you drink a half gallon of orange juice?

It is as a result of a chemical called a buffer.

Explanation:

All functioning cells, organ, blood or any other substance need to always be constant (in this case pH) and a slight change will lead to a loss of function. Fortunately, there are chemicals called buffers that act by maintaining comstant internal environment, and they work by absorbing excess hydrogen ions or releasing them depending on the acidity or alkalinity thus resisting a change in the chemical environment.

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