How does the pH affects the curdlling of milk ?

Explanation

Curds are obtained by coagulating milk by a process called curdling. The coagulation can be caused by adding small quantity of old curd. The lactobacillus present in the curd acts on the lactose and converts it into lactic acid. The increased acidity causes the milk proteins (casein) to coagulate and form curds. Hence acidic pH is required for curdling. Addition of any alkaline substance to milk will show down or not let it curdle.