Total Fat Analysis

Fat provides energy in the body, supports vital cell function, aids in the absorption of fat-soluble vitamins, and more. Total fat, as detailed on the nutrition facts label, describes the total weight of saturated, polyunsaturated, and monounsaturated fat per specified serving of a food product. Accurate fat content can help inform consumers and may lower obesity, heart disease, and other associated diseases. Food producers, regulatory agencies, and researchers are among the industries involved in fat determination.  

Complex matrices such as foods often require acid hydrolysis prior to solvent extraction to break up the matrix, which liberates bound fat and facilitates complete extraction.  

Once the sample is digested, it is extracted with a solvent, commonly petroleum ether or hexane. Total fat in foods comprises a combination of non-polar to moderately polar compounds. Thus, the polarity of the extraction solvent is the overriding factor in determining how much or how little fat will be extracted from the digested material. Extraction efficiency greatly depends on solvent choice. There are a variety of solvents referenced in total fat methodologies.  

Mojonnier Method

First established as a method for determining total fat content in dairy products, the Mojonnier method is performed by placing a sample, ethanol, and HCl in a Mojonnier tube. This mixture is then hydrolyzed under heat. A solvent mix of ethyl ether and petroleum ether is then added post-hydrolysis. The mixture is shaken vigorously and allowed to separate. Once divided, the solvent and fat layer is poured off, and the solvent is evaporated. A direct method as well, the isolated fat produced by the Mojonnier process is weighed for final determinations.

Solid Phase Extraction

SPE (Solid Phase Extraction) technology is also utilized in the determination of crude fat, based on AOAC 954.02, Fat (Crude) or Ether Extract in Animal Feed. This method is performed by the ANKOM FLEX Analyte Extractor.