GC-MS Method Used to Test for GTH in Animal By-products

The use of animal by-products (ABPs) in any phase of food production can impose great risk to the health of humans and animals alike. In response, the European Union (EU) has mandated that manufacturers in its member states mark all processed ABPs not intended for human consumption with glyceroltriheptanoate (GTH). A fat that is not found in nature, GTH is a suitable marker for all ABPs, including other fats. EU regulations state that GTH must be homogenously present in all ABP substances at a minimum concentration of 250 mg per kg of fat.

In 2010, the Joint Research Centre’s Institute for Reference Materials and Measurements in Belgium developed and validated a GC-MS method to detect the GTH marker in processed ABPs.¹ Recently, another study sought to verify instrument conditions for the routine use of this GC-MS method in laboratories, and then applied it to samples collected throughout Italy.²

Marchis et al. first validated the method by evaluating its accordance to EU regulations with respect to a variety of parameters. The GC-MS method was found to effectively detect and quantify the presence of GTH in ABPs, deeming it suitable for routine analysis. The high standard of reliability of this method was far better than those employed in other studies.

To put the validated GC-MS method to use, the researchers gathered 17 ABP samples from different regions of Italy. Of those samples, six were pure animal fat and 11 were meat and bone meal (MBM). Because it requires an additional extraction step to determine the presence of GTH, MBM is considered to be a more challenging matrix than pure animal fat.

Samples were analyzed using Thermo Scientific GC-MS instruments, a DSQ single quadrupole mass spectrometer, a FOCUS Gas Chromatograph and the AS 3000 auto-sampler. The method performance satisfied EU analytical method validation criteria.

Of the 17 samples analyzed, eight were found to be non-compliant with regulations, as their GTH concentration was below the minimum concentration required by EU law. Of the eight non-compliant samples, five were MBM and three were pure fat. In two samples, both from the same producer, the GTH amount appeared to be below the study’s lower range limit of detection.

An investigation of the manufacturers whose samples failed to meet EU regulations for GTH marking found that they did not employ validated sampling or homogenization methods. Furthermore, they did not routinely perform in-house controls, and used non-validated methods even when they did.

These findings led the researchers to conclude that regular monitoring of processed ABPs, using a validated method such as the GC-MS procedure described in this study, should take place in order to help manufacturers meet EU regulations.

References:

1 Boix, A. et al. (2010). ‘Validation of an analytical method for the determination of gylceroltriheptanoate (GTH) in processed animal by-products.’ Food Additives and Contaminants 25, 793-800.

2 Marchis, D. et al. (2013). ‘A monitoring study of glyceroltriheptanoate (GTH) in animal by-products through a validated GC-MS analytical method.’ Food Control 34, 624-629.