Fresh milk has a pH of 6. Explain why the pH changes as it turns into curd?

$pH$ changes when milk is changed to curd.

This is because, when milk changes to curd, the formation of lactic acid takes place.

$pH$ decreases because of the formation of lactic acid.

$[Acidic\uparrow pH\downarrow ]\left[H^{+}\right]\uparrow$