Question: how does milk react to acid

Ryan Cheale answered on 24 Jun 2015:

When milk and acid mix, it goes lumpy; this ‘curdling’ is due to the milk proteins clumping together into blobs (called ‘coagulation’). You could try this out by mixing lemon juice with warm milk (or you could just take my word for it). And because the human stomach contains acid far stronger than anything in your kitchen cupboard (pH 2), milk curdles very quickly after it has gone down the gullet.

We need milk to curdle for good digestion. A nice lumpy, curdled slop ensures that the swallowed milk lingers in the stomach for a while, giving it enough time for the digestive system to go to work on it. If milk didn’t curdle in the stomach, it would pass through very quickly like water, meaning that many of its nutrients will not be absorbed.