Table 1 Compounds measured and assay limitations of indicative tests
From: Evaluating the quality of feed fats and oils and their effects on pig growth performance
Indicative measure | Peroxidation compounds detected | Limitations |
|---|---|---|
PV | Peroxides and hydroperoxides | Some procedures may be too subjective. Peroxides may be undetectable in lipids exposed to >150°C. Should be used in conjunction with TBARS and AnV when assessing peroxidation. |
TBARS | Malondialdehyde | Not specific to malondialdehyde because 2-alkenals, 2,4-alkedienals can react with thiobarbituric acid. Different methodologies are used making inter-laboratory comparisons difficult. |
AnV | Aldehydes | Not specific to a particular aldehyde because 2-alkenals, 2,4-alkedienals can react with p-anisidine under acidic conditions. |
Conjugated dienes | Primary peroxidation compounds formed after a double bond rearrangement in peroxides | Less sensitive compared to PV. Carotenoids are absorbed in the same wavelength range which can cause misleading results. |
TOTOX value | Sum of AnV (or TBARS) and 2 × PV. Measures both primary and secondary peroxidation compounds. | Increases the lack of specificity inherent with AnV (or TBARS) and PV. |
Carbonyls | Secondary peroxidation compounds including aldehydes and ketones. | Lack of specificity and tendency to be influenced by non-carbonyl compounds. |
Hexanal | Specific carbonyl compound formed during the termination phase of peroxidation when linoleic acid (C18:2 n-6) or other ù-6 fatty acids are peroxidized. | Volatile at high temperatures and may provide a misleading indication of extent of peroxidation. |
DDE | Specific aldehyde derived from linoleic acid (C18:2 n-6) during peroxidation. | Complicated and expensive assay requiring gas chromatography and mass spectrophotometry. |
HNE | α, β-unsaturated lipophilic aldehyde formed during lipid peroxidation of n-6 polyunsaturated fatty acids (i.e. arachidonic and linoleic acid) | Complicated and expensive assay. |
Triacylglycerol dimers and polymers | Polymeric compounds formed during the late phases of peroxidation. | Measured with size exclusion chromatography. Limited information on their use in evaluating lipid quality and effects on animal health. |
Oxiranes | Cyclic compounds produced during peroxidation. | Assay not specific to oxiranes because it can also detect carbonyls and conjugated dienes. |
Non-elutable material | Gas–liquid chromatography procedure that estimates the non-elutable material of a lipid after a correction for glycerol. | Collectively measures most degraded chemical structures of a lipid. |