How to calculate saturation point of a solution?
Yes. But it would probably be faster to simply find some empirical data. 

You would need to:


approximate the hydrophobicity of your vitamins (for rather big molecules like vitamins, this would need some mathematical modeling, but there are some computer programs that can do this rather accurate.
this data could be used to approximate the solubility in water and probably also olive oil. But milk is quite complex, as there will be a solubility equilibrium in/between both the fat phase and the water phase. And all the salts and other compounds in the milk (and to a small degree in olive oil) will affect the solubility.


If you know A-level chemistry and know someone to help you irl (or some fab ppl here :-) ), I'd guess there's some days of work in it!