CARBON, NITROGEN AND SULFUR STABLE ISOTOPE ON BEEF FROM THREE ARGENTINE REGIONS: ORIGIN AND DIETARY HISTORY

ERNESTO GALLEGOS; HÉCTOR OSTERA

Bruselas, Bélgica

Conferencia; TRACE Final Conference; 2009

European Union - TRACE Project

The current international food market as well as consumers around the world demand new and reliable tools, independent of custody chains or documentation, for the characterization and origin certification of food commodities. These new tools aim to provide consumers the security they require with regard to quality and safety of the food they consume and contribute to the protection of producers against potential frauds.The aim of this paper is to give an evaluation of the effectiveness of C, N and S stable isotopes as a method for geographical origin and animal feeding characterization on beef in three different Argentine regions, located respectively in the provinces of Buenos Aires, Entre Ríos and Córdoba.Beef samples (500g) were processed according to the Trace SOP´s procedures. They were taken preferably from long dorsal muscles, but also samples of neck muscles were used. All samples were taken immediately or very soon after the death of the animals. Excess fat was removed with ceramic knife before storage. The samples were maintained at low temperature (2 - 4 ºC) during the first 24 hours and then stored, vacuum packed, at -20 º C and taken away from light. Geographic position of the samples was loaded into a Geographic Information System in order to establish the spatial relationship between them. A Soxhlet distillation apparatus was used for the extraction of defatted dry matter fractions from the beef samples. Stable carbon, nitrogen and sulfur stable isotopes of beef defatted dry matter were determined by conventional methods using elemental analyzer/isotope ratio mass spectrometry (EA/IRMS).The results of stable isotopes of carbon, nitrogen and sulfur led to distinguish samples from Córdoba, Entre Ríos and Buenos Aires, showing the most striking difference in the values of δ13C from Córdoba and Buenos Aires. This difference in 13C values cannot be justified by the geographical origin alone, and should be a reflection of a different diet due to the two most important feeding techniques used for cattle in Argentina: grazing and feedlot.About 20% of animals slaughtered annually in Argentina come from a feedlot fattening cattle system based on cereal grains and/or corn silage. The high availability of cereal grains and protein supplements allows achieving low-cost optimal weight gain and high profitability without any other dietary supplement.If we consider the average δ13C values for C3 and C4 terrestrial plants, and the fact that those values are reflected in the cattle beef protein with a 5 ‰ decrease, it can be inferred that the Buenos Aires cattle are feed predominantly with C3 terrestrial plants (grazing) and on the opposite, that the Córdoba cattle show a major input of C4 in their diet (feedlot technique).The lower δ15N values are from Córdoba, and Entre Ríos show the highest values. The pattern showed by the Entre Ríos samples cannot be explained by geographical or environmental differences and could be explained by other feeding technique variation, but this hypothesis has to be tested.The sulfur isotopes present the major variations between Buenos Aires and Cordoba beef, with higher values for the first. Some overlapping occurs between Entre Rios and Cordoba data.In summary, the combined use of carbon, nitrogen and sulfur isotopes alone provide enough information to determine the geographic origin of the beef and give additional information on feeding techniques.