Deciding if milk is an acid or base requires us to look at its pH. You can see by the image below that 0 is a strong acid like battery acid while something like a drain cleaner has a high base pH of 14 on the alkaline side of the scale. Cow’s milk is close to being neutral like water at a pH of about 6.7. If you read our previous article on the percent of water in milk, you might remember that milk actually contains a large portion of water. Milk is made of about 88 percent water.
Milk contains a sugar known as lactose. As fresh milk ages, bacteria breaks down the lactose to eventually form lactic acid. As the acid content increases from the lactic acid, the pH begins to decrease. The quality of the milk also begins to decrease as the pH drops below 6.5 and it will eventually sour. Milk that is fully soured will have a pH of about 4.4 [source].
Obviously, most of us drink milk until it no longer tastes fresh or smells off. However, if you are looking for milk that is closest to neutral, you want to drink the freshest quality milk.
Photo Credit: Charles Tilford