The pH level of milk is about 6. In comparison, water's pH level is 7. That is a significant difference because each level is 10 times different --either more or less-- than the level next to it.
The pH scale indicates the acidity or alkalinity of a substance. A pH of 7 is neutral. Anything below that is acidic. As the pH number becomes smaller, the acidity increases. Vinegar's pH level is 3, so it is 30 times more acidic than milk with a pH level of 6. A pH level above 7 indicates an alkalide or base. The higher the number, the more alkaline the liquid. For instance, milk of magnesia registers at pH 10. This property makes it effective at relieving acid indigestion.