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A.Boix, C.von Holst, R.Margry, S.van den Hoven, B. Verkuylen,F.Serano, S.Bellorini
JRC IRMM, European Commission

Regulation (EC) No 1774/2002 lays down rules to enable safe use of animal by-products that are fit but not intended for human consumption. It sorts animal by-products into three categories by increasing risk and requires that materials of different categories are kept separated during collection, handling and transportation. Also products derived from category 1 and category 2 need to be permanently marked, because they must not enter the feed and food chain. Marking these materials will ensure identification and traceability of products to be disposed of and will eliminate risk of fraud.
On request of DG Health and Consumer Protection (DG SANCO), the European Commission's Joint Research Centre Institute for Reference Materials and Measurements (IRMM) evaluated the characteristics of various substances that are suitable for this purpose, proposing in 2002 the use of glyceroltriheptanoate (GTH) as a potential marker for category 1 and 2 materials. It meets the requirements of the legislation; in particular it withstands extreme sterilisation conditions as applied by the rendering industry.
Experiments conducted by the IRMM and CCL Nutricontrol at laboratory scale demonstrated that the GTH withstands steam pressure heat treatment conducted at 133˚C but is not stable in raw animal by-products due to the degradation of the GTH as a result of gastrointestinal tract enzymatic activity. However, once the by-products undergo temperatures above 80˚C, the enzymatic inactivation allows GTH to be preserved. For this reason, the GTH should not be added at slaughterhouses but only at the rendering plant after a heating step above 80ºC.
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. The experimental design of the implementation study was established in close cooperation with DG SANCO, the European Fat Processors and Renderers Association (EFPRA) and Member States' experts. The concentration of GTH in the samples from the study was determined by IRMM and CCL. One of the major objectives was to establish, whether the marker can be homogeneously distributed within the animal by-products to assure that GTH is detectable at high concentration level in all positive samples.
The addition of GTH was tested for a period of one week and random samples of the final products (meat and bone meal and fat) were collected at regular intervals and analysed for the GTH content by CCL and by the IRMM.
The results of the implementation study demonstrated that GTH added in rendering plants was detectable and could be quantified at high concentration level in all positive samples. In all cases the found concentrations were far above the limit of quantification of the applied method for the detection of GTH. Therefore it can be concluded that GTH is a suitable marker for category 1 and 2 materials. In addition it was shown that analysing the samples in two laboratories applying two different methods delivers comparable results, thereby indicating the robustness of the whole procedure.