ORACLE vs. Conventional Fat Methods

Introduction

Fat determination in foodstuffs is typically carried out by either solvent extraction-based gravimetric methods such as Soxhlet and Mojonnier, or by gas chromatography (fatty acid methyl esters or FAMEs). While these methods, particularly the gas chromatography method, are considered to be the “gold standards,” they have inherent limitations.

Though ubiquitous for foodstuff production and process control applications, gravimetric methods (regarded as “crude” fat) are often not optimized for a given matrix and the results are heavily dependent on a host of experimental conditions, such as extraction time, temperature, solvent composition, and hydrolysis conditions (if applicable). Moreover, gravimetric methods can tend to overestimate fat, due to extraction of nonfat components such as low molecular weight carbohydrates, amino acids, organic acids, and glycerol. Low-moisture samples with high protein-to-fat ratios (e.g. whey protein concentrates) have been shown to be particularly susceptible to overestimation, with nonfat components comprising nearly 50% of the extraction value.

The gas chromatography method, often used for food labeling and research applications, is able to provide very detailed information about the fat composition, including the amounts of individual fatty acids. While it is viewed as being more accurate than gravimetric methods (since it is less prone to overestimation), results are heavily dependent on experimental factors such as derivatization conditions and efficiency, and column and hydrolysis conditions. Accurate quantitation can also be difficult, due both to imprecision in chromatographic peak integration as well as volatility of short-chain fatty acids.