Common Applications of Wiped Film Stills: Polyglycerides

One common use of wiped film stills is polyglyceride purification and separation.

Wiped film stills are often used in animal fat and vegetable oil processing.  There are many different applications in this industry.  This post will just deal with polyglyceride processing as a final purification step.

Many times, a manufacturer will target a particular product for an application.  These oils are used in food, cosmetics and animal care.  In order to produce a specific product, the manufacturer will take a pure fatty acid and run a reaction with glycerin to produce the desired polyglyceride mix.  The manufacturer could be targeting the monoglyceride, the diglyceride or the triglyceride.  Glycerin has three locations where a fatty acid can add, so all three molecules are made when the reaction is run. 

Once the desired mix of products is made, the chemist will halt the reaction.  At this point, the mixture contains a small amount of residual glycerin and fatty acid, along with the three polyglycerides.

Wiped film stills are very good at removing residual glycerin and fatty acid.  These molecules boil much lower than the polyglyceride products and can be easily removed from the rest of the material. 

Then, the wiped film still can be used to separate the polyglycerides into their components.  The monoglyceride is first distilled away from the diglyceride and triglyceride.  After the monoglyceride removal, the diglyceride can often be distilled away from the triglyceride.

At this point, the triglyceride can be distilled away from color and heavier compounds from the reaction mixture.  But only short and medium chain triglycerides can be distilled.  Longer chain triglycerides’ boiling points are often too high for them to be volatile, even with the high vacuum capability of wiped film stills.  In these cases, it is necessary to clean up the triglyceride product with another method.