The determination of the 2-thiobarbituric acid value is one of several analytical methods
for the evaluation of the degree of oxidation of vegetable oils, fish oils and animal fats,
particularly those containing linolenic acid and mre unsaturated fatty acids.
2-thiobarbituric acid forms red-coloured products with malonaldehyde (l), some
polyunsaturated aldehydes (2), dioxolanes and furan derivatives. The intensity of
coloration is correlated with the rancidity degree of fats and oils.
In the modification described the direct determination of total reactive substances is
used, without previous isolation of the volatile fraction. The 2-thiobarbituric acid (TEN)-
value, measured at 530 nm, is particularly useful for measuring oxidative changes in fats
and oils containing fatty acids of greater unsaturation than linoleic acid.
secondary oxidation products react with TBA forming cmdensation products with absorption
maxima at 450 m and 530 nm. The latter maximum is measured in this direct procedure while
the analysis of substances absorbing at 450 nm requires a different procedure (2).
'Ihe method was preliminarily tested in six laboratories, each laboratory using its am samples; on the basis of these experiments the final text was prepared, and the method
submitted for interlaboratory testing.