In a typical procedure, a known amount of sample dissolved in an organic solvent (often isopropanol) and titrated with a solution of alcoholic potassium hydroxide (KOH) of known concentration using phenolphthalein as a colour indicator.
[5] A liquid fat sample combined with neutralized 95% ethanol is titrated with standardized sodium hydroxide of 0.1 eq/L normality to a phenolphthalein endpoint.
Such reaction occurs by the action of lipase enzyme and it is an indicator of inadequate processing and storage conditions.
The source of the enzyme can be the tissue from which the oil or fat was extracted or it can be a contaminant from other cells including microorganisms.
This is because the FFAs produced can corrode automotive parts, hence these limits protect vehicle engines and fuel tanks.