Curdling of milk is a chemical change

Yes, curdling of milk is a chemical change. Because Milk is converted into curd or yogurt by the process of fermentation. Milk consists of globular proteins called casein. The curd forms because of the chemical reaction between the lactic acid bacteria and casein. During fermentation, the bacteria use enzymes to produce energy (ATP) from lactose.
Since fermentation is occurring, a chemical change is also occurring.
Therefore curdling of milk is a chemical change.