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S. van den Hoven1, B. Verkuylen1, R. Margry1, A. Boix2, S.Bellorini2, F.Serano2  and C. von Holst2
1 CCL Nutricontrol, Veghel, the Netherlands
2 Joint Research Centre, Institute for Reference Materials and Measurements (JRC-IRMM),
Geel, Belgium

Since May 1 2003, products derived from animal by-products category 1 and 2 need to be marked permanently according to Regulation (EC) No 1774/2002, because these products must not enter the feed and food chain. Marking these materials will ensure identification and traceability of products to be disposed of.

In 2002 Joint Research Centre Institute for Reference Materials and Measurements (JCR- IRMM) proposed the use of glyceroltriheptanoate (GTH) as a potential marker for category 1 and 2 materials. GTH is a fat with three n-heptanoic acids esterified with glycerol. This substance is not found in nature, but is regarded as safe. It has several applications in the food industry, for example as a marker in the butter market. GTH is stable during extreme sterilisation conditions and during storage for at least two years.
An implementation study for the use of GTH as a marker for animal by-products was carried out at 10 European rendering plants to evaluate the feasibility of the marker system in practical circumstances. At the rendering plants GTH was added to the process for a period of five continuous days in a dosage of 100 mg/kg of raw material. The GTH was introduced into the process after a first heating step of 80 C and before a homogenisation step. Samples of the final products (MBM and rendered fat) were collected and analysed independently by CCL and JRC-IRMM.

The analytical method used by CCL is based on extracting the sample with petroleum ether 40-70, clean-up on a silica column and measuring the GTH content with GC coupled to a flame ionisation detector (FID). The method of JRC-IRMM is based on extraction with n- hexane; clean-up utilising solid phase extraction cartridges and measuring the GTH content with gas chromatography coupled to mass spectrometry (GC-MS).

The results of the implementation study demonstrate that GTH added in rendering plants was detectable and that in practice, a minimum concentration of 250 mg/kg fat to be achieved in the processed product, is efficient as marker for category 1 and 2 materials. FID can be used as detector when utilised for the determination of the concentration of GTH in target materials (i.e. material from cat. 1 and 2) containing GTH around the target concentration. However, confirmation of the presence or absence of GTH in non-targeted materials, such as those belonging to category 3, require the use of mass spectrometry as detector.

Keywords:
Animal by-products; GTH; marker; MBM; fat