What is happening to the temperature of the substance before and after the phase changes?

First off, you must realize that the phase changes are marked by the points B and D on the graph. They are level because all of the energy (or heat) being added is being consumed by the physical process. So The temperature is increasing before the phase change, and after the phase change. The moments before and after are represented by points A, C, and E.

The dispersed phase is liquid and dispersed medium in milk is liquid