Hydrogenated oils are solid or semi-solid food grade oils which are characterized by their iodine value (IV), or degree of fatty acid unsaturation. Hydrogenated oils with an IV of ≤4 are considered fully hydrogenated (FHOs), whereas those with an IV of &gt;4 are considered partially hydrogenated (PHOs). In 2015, the United States Food and Drug Administration determined that PHOs are no longer generally recognized as safe (GRAS) for any use in human food, making the analytical discrimination between FHOs and PHOs a regulatory concern. The IV of an edible oil may be determined by titration or calculation based on fatty acid composition. The objective of this study was to compare the titration and calculation approaches for the accurate determination of IV in hydrogenated oils. Seven samples of hydrogenated oil were analyzed according to Recommended Practice Cd 1c-85 (calculation) of the American Oil Chemists’ Society (AOCS) as well as the two titration AOCS Official Methods Cd 1b-87 and Cd 1d-92. Standard addition experiments were performed using triolein (cis-9-C18:1 triglyceride) to determine the true IV of the oil samples, which varied from 0.1–4.5. IVs determined according to AOCS Cd 1c-85 (calculation) were statistically similar to the true IVs for all of the samples except one soybean oil, whereas for the two titration methods, IVs were significantly greater than the true IVs for all of the samples except coconut oil. Additional limitations of the titration methods included cumbersome handling of large volumes of reagents, extensive heating and shaking of samples, and the tendency for oils to curdle upon addition of reagent. Although each of the methods successfully discriminated between FHOs and PHOs, AOCS Cd 1c-85 (calculation) provided the most accurate and repeatable determinations of IV.<br/>

Determination of iodine value (IV) in hydrogenated oils

254th National Meeting (2017)

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