Lipids anisidine value

Other traditional methods available for monitoring the extent of lipid oxidation include the Anisidine value, the Kreis test (Mehlenbacher, 1960), methods based on the carbonyl content of oxidized fats (Henick et al., 1954 Lillard and Day, 1961), and measurement of oxygen uptake either by manometry or polarography (Tappel, 1955 Hamilton and Tappel, 1963). 

Despite it limitations, the TBA test provides an excellent means for evaluating lipid oxidation in foods, especially on a comparative basis. However, its use in bulk oils is less common than the so-called para-anisidine value (p-AnV) detailed below. 

Carbonyl compounds in oxidized lipids are the secondary oxidation products resulting from the decomposition of the hydroperoxides. They can be quantified by the reaction with 2,4-dinitrophenylhydrazine and the resulting colored hydrazones are measured spectrophotometrically at 430-460 nm. The carbonyl value is directly related to sensory evaluation, because many of the carbonyl molecules are those responsible for off-flavor in oxidized oil. The anisidine value is a measure of carbonyl compounds that have medium molecular weight and are less volatile (Frankel 1998). It can be used to discover something about the prior oxidation or processing history of an oil. 

Lipid oxidation during frozen storage of fat and medium-fat fish is an important quality problem, primarily due to effects on sensory properties such as rancid off-odor (appearing earlier than off-flavor), orange-brown discoloration, and texture changes. Changes in peroxide value (PV) and carbonyl compounds such as anisidine value (AsV), benzidine value, carbonyl value, and thiobarbituric acid (TEA) proceed... 

Many methods have been developed to access the extent of oxidative deterioration, which are related to the measurement of the concentration of primary or secondary oxidation products or of both. The most commonly used are peroxide value (PV) that measures volumetrically the concentration of hydroperoxides, anisidine value (AV), spectrophotometric measurement in the UV region and gas chromatographic (GC) analysis for volatile compounds. Vibrational spectroscopy, because of its high content in molecular structure information, has also been considered to be useful for the fast measurement of lipid oxidation. In contrast to the time consuming chromatographic methods, modem techniques of IR and Raman spectrometry are rapid and do not require any sample preparation steps prior to analysis. These techniques have been used to monitor oil oxidation under moderate and accelerated conditions and the major band changes have been interpreted. ... 

A disadvantage of using such methods is that the fat phase has to be extracted from the food product before the analysis can be performed, and so it can be argued that the extracted fat phase does not fully represent the lipid phase as present within the food product. This apphes especially to measurements of the decomposition products of the lipid phase by the peroxide and anisidine values, which quantify the more volatile and/or polar decomposition products. In our experience, the percent free fatty acids value and the quantification of total TAG in conjunction with headspace analysis mimics extremely well the results of evaluation by a sensory panel (O. Bode, personal commimication). 

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