Buffer capacity of different types of milk

Currently I am tasked with designing an experiment that that I will have to perform in 2-4 weeks, but I don't have to decide on on a topic soon. I was thinking of performing an acidometric titration (most likely with hydrochloric acid) of different types of milk such as skim, organic, fat free and from it make a $\mathrm{pH}$ curve. From here I would see how these different types of milk acted as buffers relative to each other, by analyzing their buffer regions in the $\mathrm{pH}$ curve.


I have heard that milk can act as a buffer, but I cannot find information about what buffers regulate the $\mathrm{pH}$ the most. 
I would greatly appreciate if any of you could share your knowledge or some sources about buffers constitute milk.


