Oxidation Analysis of Nutraceutical Oils

Oxidation Graph Oxidation over time as measured by Peroxide Value(PV), Anisidine Value(AV) and Totox Value.

The degree of oxidation is an essential factor of the quality of a fat or oil. Lipids are chemically unstable and will readily undergo free-radical chain reactions that not only deteriorate the lipids but also produce oxidative fragments, some of which are volatile and are perceived as the off-flavours of rancidity. Oxidation is a complex series of reactions. Oxidation generates a sequence of breakdown products, starting with primary oxidation products (peroxide value, dienes, free fatty acids) then secondary products (carbonyls, aldehydes, trienes) and then tertiary products.

Food oils (including marine oils, food oils, etc.) contain many polyunsaturated fatty acids (PUFA) which are highly susceptible to oxidation. These unsaturated fatty acids have reactive double bonds between their carbon atoms, whereas saturated fats have no double bonds, so they oxidise more slowly. Oxidation may be accelerated by a variety of factors including the presence of oxygen, oxidizing agents (metal catalysts), enzymes (iron-centered atom lipoxygenase), photo-oxidation, heat and more.

Measuring Oxidation:

Oxidation of fats and oils testing for the primary and secondary breakdown products. Lipid Analytical Laboratories Inc. offers peroxide value (PV), anisidine value (AV) and acid value (AcV) testing based on qualified methods for the oxidative analysis of marine oils and refined food oils.

Peroxide Value (PV):

Primary oxidation in oil mainly forms hydroperoxides, which are measured by the PV. In general, the lower the PV, the lower the oxidation state of the oil and the better the quality of the oil. Hydroperoxides are reacted with iodide ions to form iodine and the PV is determined by titration of the liberated iodine with thiosulphate using starch as an indicator.

Anisidine Value (AV):

The secondary stage of oxidation occurs when the hydroperoxides decompose to form carbonyls and other compounds, in particular aldehydes. These are what gives the oil a rancid smell, and they are measured by the AV. The analysis method for AV determines the amount of aldehydes (principally 2-alkenals and 2,4-dienals) in oils and fats by reaction of these compounds with the p-Anisidine and measuring the absorbance at 350 nm with a spectrophotometer.

Acid Value (AcV):

The acid value is a measure of the free fatty acids (FFA) present in the fat or oil. Increment of free fatty acids indicates hydrolysis of triglycerides (or phospholipids). The method to determine AV in fats and oils is based on a titration in ethanol using phenolphthalein as indicator.

SafTest Analysis:

For simple and rapid testing, SafTest analysis offers an alternative method for determining the PV and AcV of fats or oils in solid/dry materials. The SafTest methods are qualified and in alignment with AOCS standardized testing methods for oxidation.

Sample Matrices:

The oxidative state of lipids can be tested in materials such as marine oils, refined food oils, etc.

Sample Requirements:

  • Liquid medium (e.g. oils)
  • Solid/dry foods, tissues
  • Please contact with regards to your specific medium.

Data Reporting:

  • CoA (pdf.) provided for sample analysis.
  • Data reported as: μg/g and % by weight for either total phospholipids or by individual phospholipids species.
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