Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/1998
Publication Date: N/A
Interpretive Summary: Free fatty acid (FFA) content in oil is an important quality marker for oil in oilseed and throughout the oilseed process. The seed is priced with a penalty if FFA is higher than 1.8 % or with a premium when FFA is low. Cottonseed samples previously collected from an oil mill showed large variations in FFA. These variations are apparently strongly associated with the thermal history of the samples. A systematic study demonstrated that the AOCS Official Method Aa 6-38 for FFA determination is reproducible but tends to underestimate the amount of FFA by 11.5%. This will translate into artificially higher seed price and greater refining loss than what is expected to the oil mill operators. Recommendations for more accurate determination of FFA in cottonseed are given.
Technical Abstract: The official AOCS method for the determination of free fatty acid (FFA) in cottonseed requires dehulling the seed, grinding the meats with a 12-blade food processor and extracting the ground meats in a butt tube with three portions of room temperature petroleum ether. The extracted oil after desolventization is then titrated with NaOH to the end point of phenolphthalein in a mixed solvent of isopropanol and hexane. Our study showed that this procedure tends to under-estimate the amount of FFA present in the oil of the cottonseed by as much as 11.5%. It was also found that to obtain consistent and accurate FFA content: A desirable particle size is smaller than 10 mesh (preferably < 14 mesh), minimum extraction temperature should be no less than 40 C (preferably greater than 50 C), and the extraction time should be longer than 2 hours in a Soxhlet extractor.