Saponification number

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Fat saponification

The saponification number ( VZ ) is a key figure for the chemical characterization of fats and oils . It is used for their purity testing and quality control. The saponification number is a measure of the acids bound and freely occurring in one gram of fat . It indicates how much potassium hydroxide (in mg ) is necessary to neutralize the free acids contained in 1 g of fat and to split the existing ester bonds ( saponification ). The smaller the mean molar mass of a fat (i.e. the more short-chain fatty acids it contains), the greater the saponification number. In practice it is a back titration . The excess fat sample is refluxed with ethanolic potassium hydroxide solution and the unused amount of KOH is determined acidimetrically by titration with hydrochloric acid in the presence of a color indicator .

Typical saponification numbers of various substances

substance Area
from to
Rose oil 008.0 021.0
Beeswax 070 080
China wax 073 093
Rice bran wax 075 120
Castor wax 175 185
castor oil 186 203
Nettle seed oil 186.8 186.8
Rose hip oil 189 193
Cocoa butter 194.0 196.0
Isopropyl myristate 202 212
Japan wax 206 238
Clarified butter 218 235

Calculation examples

  • C 47 H 90 O 6 (molar mass 751.2) “require” 3 mol of KOH = 168300 mg. 224 mg KOH are required for 1 g fat. VZ = 224.

  • C 51 H 98 O 6 (molar mass 807.3) “require” 3 mol of KOH = 168300 mg. 209 mg KOH are required for 1 g fat. VZ = 209.

Web links

Individual evidence

  1. ^ Siegfried Hauptmann : Organic Chemistry , 2nd revised edition, VEB Deutscher Verlag für Grundstoffindustrie, Leipzig, 1985, p. 654, ISBN 3-342-00280-8 .
  2. ↑ Reinhard Mattisek, Gabriele Steiner, Markus Fischer: Food Analysis . 4th edition. Springer, Berlin 2010, ISBN 978-3-540-92205-6 .
  3. ^ Organikum , Wiley-VCH Verlag GmbH, 23rd edition, 2009, pp. 498-499, ISBN 978-3-527-32292-3 .
  4. ↑ Bruno and Paschke: Detection of foreign fats in cocoa butter , magazine for food investigation and research issue 60, number 3 / September 1930 doi : 10.1007 / BF01664060 .