Anisidine number

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The anisidine number ( AnZ ) is a fat index and is used for the chemical characterization of fats .

It is a measure of the content of α, β-unsaturated aldehydes in fats and oils. These aldehydes are secondary degradation products through autoxidation . There are mainly 2-alkenals and 2,4-dienals, but other oxo compounds in fat can also influence the result. In addition, no distinction is made between volatile and non-volatile aldehydes. The anisidine number thus provides information about the shelf life of fats.

To determine the anisidine number, the sample dissolved in isooctane is reacted with a p - anisidine solution (0.25% in glacial acetic acid ). Aldehydes react with the p- anisidine to form an azomethine ( Schiff base ), which has an absorption maximum at 350 nm. Unsaturated aldehydes form more absorbent products than saturated aldehydes.

While the peroxide value (PV) to the refining to decrease the fat, the anisidine value increases. This means that even after refining, fats can be identified that have already been damaged by oxidation. Typically a perfect oil should have an anisidine number of <6 (mostly between 0 and 3). Values ​​above 10 are usually oxidatively spoiled fat or oil. Olive oil is an exception . The anisidine number is typically higher here.

Together with the peroxide number, the so-called Totox number can be calculated using the anisidine number (Totox = AnZ + 2 · POZ).

Individual evidence

  1. ↑ a b M. H. Gordon: Understanding and Measuring the Shelf-Life of Food . Factors affecting lipid oxidation. Ed .: R. Steele. Woodhead Publishing, 2004, ISBN 978-1-85573-732-7 , pp. 136 ( limited preview in Google Book search).
  2. ↑ Frede, Wolfgang: Handbook for food chemists: Food - Commodities - Cosmetics - Feed . Springer Berlin Heidelberg, Berlin, Heidelberg 2010, ISBN 978-3-642-01685-1 , pp. 672 ( limited preview in Google Book search).
  3. ↑ Reinhard Matissek, Gabriele Steiner, Markus Fischer: Food analysis . 6th edition. Springer-Verlag, Berlin 2018, ISBN 978-3-662-55721-1 ( limited preview in Google book search).
  4. ↑ Notes on determining the Totox number and the DGF standard methods C-VI 6a (02) and C-VI 6e (05) for determining the peroxide number and the anisidine number. (PDF) In: German Society for Fat Science eV July 2012, accessed on March 14, 2019 .