Values (commonly abbreviated to TBA values) used for assessing lipid oxidation in foods and other biological systems, using thiobarbituric acid (TBA). Two molecules of TBA react with one molecule of malonaldehyde to produce a red pigment; the amount of pigment produced is measured spectrophotometrically. Extent of lipid oxidation, reported as the TBA value, is expressed as milligrams of malonaldehyde equivalents per kilogram of sample, or as micromoles of malonaldehyde equivalents per gram of sample. The TBA test may be performed directly on the sample, its extracts or distillate.