Other methods

Introduction

Apart from the gravimetric procedures, other approaches have been reported in the literature on fat methodology. Some of them will be briefly mentioned here but, except for gas chromatography, are not further discussed in this module.

Gas liquid chromatography

The most important one is the measurement of triglycerides based on the measurement of total fatty acids by gas liquid chromatography (glc). The total amount of fatty acids is then converted to triglyceride equivalents. Measurement of total fat by glc is mandatory for labeling purposes. The advantage of this approach above gravimetric procedures is the selectiveness (lack of interference from other compounds such as vitamins, sterols etc that are co-extracted in organic solvents). For the determination of the fatty acid profile, first total fat is extracted by a mild fat extraction method (e.g. Folch extraction). After that, the fatty acid profile of the extracted fat is analyzed. Analysis of fatty acids by gas chromatography will be discussed in the following part of this module.

Infrared spectroscopy

This is based on the absorption of energy of the C=O bond in the fat molecule at 5.72 µm (infrared region). This approach is more selective than the classical gravimetric procedures. It is often used for dairy products.

Volumetric methods

Has been used often for milk fat (Babcock and Gerber procedures).

Specific gravity

This is known as the Foss-Let technique: fat is extracted into tetrachloroethylene and the change in specific gravity is measured in a magnetic float cell. Has particularly been evaluated in meat and meat products.