The present invention relates to a method and arrangement for hydrolyzing infant formula. The method comprises the steps of providing infant formula in a product pipe, performing a pH measurement of the infant formula in the product pipe, adjusting the pH of the infant formula in the product pipe, based on the measured pH in the product pipe, by inserting a caustic solution to the infant formula in the product pipe, inserting an enzyme to the infant formula in the product pipe, and transferring and storing the infant formula in a holding tank.