Stable isotope databases for European food products

Stable isotope ratio analysis (SIRA) of the socalled bioelements (H,C,N,O,S) and the heavy element strontium is applied for food authenticity control and for geographical origin assignment of food products since about 30 years. The first official methods eg for honey and fruit juices have been acknowledged in 1978 and 1981 by AOAC. In 1990 the EU decided to install an official database for wine stable isotope parameters from all wine producing member states, at the same time accepting the H-NMR (Nuclear Magnetic Resonance Spectroscopy) analysis of wine ethanol as official method. This database now contains the stable isotope data for hydrogen, carbon and oxygen (measured by IRMS= Isotope Ratio Mass Spectrometry) from wine ethanol and wine water of about 1000 authentic samples per year, which have now been collected for 17 years from several countries. The same stable isotope methods as for wine are applied for fruit juices as well, therefore the Schutzgemeinschaft der Fruchtsaftindustrie (SGF) e.V. in Nieder-Olm compiled a fruit juice database since 1991, which has been further extended during an EU project (“PURE JUICE”) from 2002-2005 and is now accessible via internet by the members of SGF, PURE JUICE participants and public control laboratories (www.purejuice.org). The AG Stabilisotopenanalytik of the GDCh has recently installed a stable isotope database for fruit juices as well (www.agstabilisotopen.org), which should be extended to other products, but is at present only accessible for members of this group. In a recent EU project “TRACE” (www.trace.eu.org) stable isotope data are collected for a variety of food commodities, as honey, cereals, lamb, beef, olive oil, and mineral water. At the same time surface water and soil samples are taken and their stable isotope (and other) parameters analysed as well. ______________________________________________________ 1 isolab GmbH, Laboratorium für Stabile Isotope, Woelkestraße 9/I, 85301 Schweitenkirchen, and TU München, Center of Food and Life Sciences Weihenstephan, 85350 Freising, Germany [email protected] The aim of this project is to model and finally to predict stable isotope data for food commodities from the geographical, climatic, geological, botanical and hydrological information available even for regions where no authentic samples are accessible. If this works, the efforts for compiling databases of stable isotope data could be remarkably reduced. In case of wood stable isotope data for several regions have been collected since a long time by climatologic researchers, as they use hydrogen and oxygen isotopes of tree ring cellulose to obtain information about the climate of the past. The substance analysed usually is pure α-cellulose, which has to be prepared from raw wood by laborious preparation methods. A recent paper has indicated that it might be possible to replace this procedure by a less time consuming method applying the hydrogen isotope ratio of methyl groups instead of the cellulose. Finally, it should be mentioned that hydrological research has produced data collections of water stable isotope data (precipitation and ground water) from many regions and over about 40 years, especially in Europe, but for other regions of the world, too. The information gathered in those databases could be very useful for geographical origin assignment of wood sample. 1 Basic information about stable isotope analysis Chemicals elements occur in nature as mixtures of two or more stable isotopes. Especially for the light elements H,C,N,O and S, the so called bio elements, as they form the basis of all living matter, the light isotope is by far more abundant as the heavy isotope(s). In case of carbon, the isotope C has about 98.9 %, the heavier isotope C about 1.1 % natural abundance. The mean natural isotopic ratio (eg C/C) of these bio elements is not absolutely constant, it shows distinct and systematic variations due to physical and biochemical isotopic fractionation, which can be used to conclude about the history and provenance of biochemical and/or biological material from different sources, even if it is chemically pure and/or identical (Kelly et al., 2005, Rossmann 2001). This possibility has been used for questions of geology, archaeology, forensics, environmental sciences and food authenticity.