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Crude fat



This method quantifies the amount of crude fat (fats, oils, pigments, and other fat soluble substances) in dried forages and mixed feeds using the Randall modification of the standard Soxhlet extraction.  The extraction process includes submerging the test portion into boiling ethyl ether and then lowering the solvent below the sample for a continuous flow of condensed solvent.  The solvent is evaporated and recovered by condensation.  The resulting crude fat residue is determined gravimetrically after drying. The method has a detection limit of 0.25 %.

Samples high in carbohydrates, urea, lactic acid, glycerol, and other water soluble components should undergo water extraction in order to avoid false high values.  Water extraction must be requested by the client at the time of sample submission.

Sample amount required:   15 g

Questions concerning limited sample size can be answered by the UC Davis Analytical Laboratory.

AOAC Official Method 2003.05, Crude Fat in Feeds, Cereal Grains, and Forages, in Official Methods of Analysis of AOAC International, 18th edition (2006), Chapter 4, pp. 40-42, AOAC International, Arlington, VA.