This International Standard specifies a method for the accurate determination of isolated trans bonds in natural or processed long-chain fatty acids, fatty acid esters and triglycerides with trans isomer levels W 5 %.The method is not applicable, or is applicable only with specific precautions, to. fats and oils containing high levels (over 5 %) of conjugated unsaturation (e.g. tung oil),. materials containing functional groups which modify the intensity of the C-H deformation about the trans double bond [e.g. castor oil containing ricinoleic acid or its geometrical isomer, ricinelaidic acid(12-hydroxy-9-octadecenoic acid)],. mixed triglycerides having long