Q:

Shea Stearin Extraction by Dry Fractionation

I have been able fractionate palm oil and extract palm stearin using the following method:

Melt the palm oil (over 80 °C)
Keep the melted oil at 33.5 °C for 24 hours (using an immersion circulated water bath) 

At this point I was able observe crystals being formed. I assume they were palm stearin crystals.

Centrifuge to separate the crystals to obtain palm stearin.

I was able fractionate almost 30 % crystals by weight.

However the same process did not really hold true while processing the shea butter to fractionate shea stearin. After Step 2, it was still in liquid form and there was no visible crystal formation. I'm further considering seeding (with crystals) or playing with the time and temperature variations. 
How can I modify my approach to promote stearin crystal formation in shea butter?

A:

Shea butter is a complex combination of esters:

(Wikipedia). The overall ratio of oleic to stearic acids is about 2/1, but statistically, there will a little of the high melting stearic, more of the 2 stearic to 1 oleic; much more of the 2 oleic to 1 stearic, and a lot of all oleic ester. The melting point of shea butter is low (body temperature) and so if it does not precipitate out the tristearin even at room temperature, you will have to do something different.
A fractional crystallization involving higher temperatures would use a poor solvent for the tristearin (mp ~ 72C), like ethanol. The oleic esters will be more soluble. Make a 20-30% solution in hot ethanol (be careful!!) and let it cool. Experimenting with similar alcohols (propyl, isopropyl, and perhaps with a bit of water added (~5-10%) could give better results. 
Oiling out is a common problem in trying to crystallize organic compounds. 

