PoultryTech Newsletter, Volume 28, Issue 1, Spring, 2016
Removal of Free Fatty Acids from Rendered Oil

Daniel Sabo, Ph.D., research scientist, discusses his exploratory research project that is investigating the use of magnetic nanoparticles for removal of free fatty acids from rendered oil to improve oil quality and shelf life.


Q: PoultryTech – What is the goal of the project?


A: Sabo – Rendered oil from poultry byproducts is typically used for animal feed. Secondary protein nutrients (SPN), also called dissolved air floatation (DAF) skimmings, have a high oil content, but also contain large amounts of free fatty acids (FFAs), particularly after rendering. This limits the usefulness of SPN as a raw material for the range of products typically supplied. Hexane is often used to extract residual oil, but the method does not separate the oil from the FFAs.


The goal of the project is to develop a low-cost and efficient method to remove FFAs from the oil using magnetic nanoparticles (MNPs).


Q: PoultryTech – How does the method work?


A: Sabo – The MNPs remove the FFAs from oil based on a chemisorption principle. Chemisorption produces a chemical reaction between a surface and any substance on the surface.


In this case, the MNPs collect the FFAs in the oil. Specifically, the surface of the MNPs is known to exhibit a high affinity for carboxylic acids, including fatty acids. This high affinity is the property that is exploited to remove FFAs from oil systems. All FFAs include a specific property that will chemisorb to the particle surface. Once the particles are removed from the oil using a magnet, the FFAs attached to the surface will also be removed, thus lowering the FFA level in the oil.


Q: PoultryTech – What are the advantages of the method?


A: Sabo – We use MNPs that are synthesized under very controlled conditions to capture FFAs efficiently from oil systems. By controlling the synthesis of the MNPs a higher surface area-to-volume ratio is achieved, resulting in higher FFA removal. The magnetic response of the nanoparticles allows for faster capture from the oil.


An added benefit is that it is easy to regenerate the surface of the MNPs, and the chemical stability of the nanoparticles allows the MNPs to be reused more times before replacement MNPs are required.


Another advantage of this method is the ability to remove FFAs from oil systems without the use of harsh chemicals, which eliminates traditional waste streams. Since FFAs have intrinsic value themselves, the ability to strip them from the nanoparticles and use them in other industries is beneficial.


Q: PoultryTech – What are the initial testing results?


A: Sabo – We have tested the MNPs with a variety of oils including olive oil, a low-FFA fat, and brown grease. In each, we were able to improve the percentage of FFAs removed by using the MNPs. For poultry processing, in particular, the brown grease FFA level was reduced from an unacceptable level of 5% to a desired level of 3.6% with only a 4% weight loading of MNPs. We were able to reduce the FFA level even more with a 10% weight loading of MNPs, resulting in a 55% FFA removal rate (5% down to 2.3%). The industry standard states FFA content has to be below 4% for stabilized pet food poultry fat. The lower the FFA, the better for shelf life and oil quality.


We are excited that our initial tests showed successful removal of FFA from poultry oil, demonstrating that it is possible to take a low-quality product and turn it into a higher value product using MNPs. In fact, we have filed an invention disclosure on the method.


Q: PoultryTech – What are the project’s next steps?


A: Sabo – We just recently discovered that heating the oil system almost doubled its FFA removal capacity, so we plan to test the effect of temperature on system optimization. We also plan to test the effect of particle size on the adsorption capacity of the MNP system and finalize the optimization process. Lastly, we hope to scale up the testing and begin prototype development of a FFA removal system using MNPs.


Q: PoultryTech – What are the potential benefits for industry?


A: Sabo – The ability to remove problematic FFAs from rendered oil and DAF skimmings would provide renderers more product mix flexibility. The processors would, in turn, receive better quality animal feed while also having a byproduct material with a higher value.


The extraction of FFAs would provide a significant benefit, particularly for the poultry and allied industries. Notably, from 2011-2014, the average price of poultry oil decreased from $990 per metric ton to $660. It would be a benefit to the renderer to be able to have more options regarding markets for the rendered oil.



Daniel Sabo, Ph.D., ATRP Research Scientist




Before (left) and after (right) photos of brown grease sample testing. Researchers successfully used magnetic nanoparticles to reduce free fatty acid levels and improve oil quality.

Before (left) and after (right) photos of brown grease sample testing. Researchers successfully used magnetic nanoparticles to reduce free fatty acid levels and improve oil quality.