Elsevier

Food Control

Volume 67, September 2016, Pages 144-154
Food Control

Verifying the geographical origin of poultry: The application of stable isotope and trace element (SITE) analysis

https://doi.org/10.1016/j.foodcont.2016.02.018Get rights and content

Highlights

  • Best analytical strategy for accurately verifying geographical origin.

  • This research addresses a need for valid data sets on the geographical origin of poultry.

  • Application of δ18O‰ tissue water analysis has been shown to be significantly affected by storage conditions.

  • Analysis performed on 384 chicken samples originating from Europe, China, Brazil, Chile, Thailand and Argentina.

Abstract

Stable isotope and elemental analysis, together with statistical processing of the resultant data has been used to determine the geographical origin of poultry and hence provide a means to verify poultry labels originating from major producing countries/regions. Multivariate statistical analysis has demonstrated that 18 variables, including carbon, hydrogen and nitrogen stable isotope ratios and elemental concentrations of magnesium, thallium, rubidium and molybdenum, are important parameters in poultry origin determination. Using cross-validated discriminant analysis 88.3% of poultry geographical origins were correctly classified (n = 339). Individual correct-classification rates were as follows; China, 100% (n = 36); Brazil, 94.1% (n = 101); Europe 92% (n = 87); Chile 82.6% (n = 46); Thailand, 70.3% (n = 46) and Argentina 50% (n = 10). The main identification errors were associated with miss-classification of Argentinean samples with those originating from Chile and Thailand. Carbon stable isotope ratios of chicken meat indicate the quantity of maize in the diet and this leads to useful discrimination between a large proportion of European poultry and poultry reared in locations such as South America, Thailand and China where maize feeding predominates. The use of poultry carbon isotope values as a simple ‘screening’ parameter to differentiate European poultry meat from other major importers is not as reliable as for the differentiation of European and South American beef. However carbon isotope ratios will be useful in most instances to corroborate suspicion of mislabelling of non corn-fed European poultry. The stable isotopes of hydrogen and oxygen in chicken meat change in a similar way to surface waters around the globe. Our findings support the hypothesis that the global isotopic variation of stable isotopes in drinking water and feed are transferred into animal tissue and can be used to help establish an animal's geographic origin. This is a significant finding and mirrors our observations for beef skeletal muscle δ2H ‰ and δ18O ‰ values. These systematic variations can be exploited to give a ‘low-resolution’ indication of an animal's geographic origin (e.g. Northern Europe versus the tropics).

Introduction

There is growing enthusiasm among consumers for high quality food with a clear regional identity. Motivations vary from (a) patriotism; (b) specific culinary, organoleptic qualities, or purported health benefits associated with regional products; (c) a decreased confidence in the quality and safety of foods produced outside their local region, country or the EU or (d) concern about animal welfare, ‘environmentally friendly’ production methods and ‘food miles’. Food scares such as chicken influenza and the malpractices of some international food producers (e.g. use of banned nitrofurans in chicken production) have added to public sensitivity regarding the validity of poultry origin labelling (Kelly, 2003). As a result of specific legislation (e.g. Food Information Regulations, EU 1169/2011) and general public concerns, there is a need for reliable analytical methods that can verify origin labels describing where poultry has been reared prior to slaughter. In addition, analytical identification of meat origin from outside the EU is a valuable tool for European enforcement authorities.

A common theme of food authentication studies is the requirement for a database of genuine samples to which a questionable test sample can be compared to establish its authenticity. Geographical origin determination is no exception, but the need to source agricultural products from a wide range of countries is time consuming and costly. Furthermore, in order to constrain an authenticity parameter such as geographical origin there may be a requirement for a large number of independent variables to be measured and statistically ‘screened’ in order to identify key tracers that differentiate the regions or countries of interest. There have been a number of literature reviews dedicated entirely (or at least in part) to the application of multi-element and multi-isotope analysis to the determination of food provenance. These include Horn et al., 1997, Anklam, 1998, Rossmann, 2001, Kelly, 2003, Kelly et al., 2005 and Hölzl, Horn, Rossmann, and Rummel (2004). In addition the multivariate statistical techniques used, in combination with a wide range of analytical methods including multi-element and isotopic analysis, to classify food products according to their geographical and varietal origin has been critically reviewed by Tzouros and Arvanitoyannis (2001). Measuring elemental concentrations and isotopic variation in premium regional products is arguably the best analytical strategy for accurately verifying geographical origin.

There have only been two publications relating specifically to the determination of the geographical origin of poultry on relatively small sample sets. Franke, Haldimann et al., (2007) measured the concentrations of a total of 72 different elements in 25 poultry breast fillets originating from Switzerland (n = 7), France (n = 2), Germany (n = 3), Hungary (n = 6), Brazil (n = 4), and Thailand (n = 3), by inductively coupled plasma high resolution mass spectrometry (ICP-HRMS). Analysis of variance was used to identify elements that were significantly different between the countries of origin examined. Mean concentrations of four elements; arsenic, sodium, rubidium and thallium were found to be significantly different. However, the discrimination power among countries depends on the numbers of observations, which were low.

Franke, Koslitz et al., (2007) also report strontium isotope data for 22 poultry samples and δ18O ‰ data for water extracted from 78 poultry samples. The average values of 87Sr/86Sr were numerically lowest for poultry meat samples from Germany and highest for samples from Hungary. However, the pairwise comparison among means (with conservative Bonferoni adjustment) did not specify any individual differentiation. Analysis of variance of the poultry breast meat tissue water δ18O ‰ showed significant differences between Brazil, Germany, Hungary and Switzerland. However, the use of tissue water for δ18O ‰ analysis has been shown to be significantly affected by storage conditions. Increasing open storage times, including post-mortem hanging or maturing result in decreasing meat juice yield, increasing weight loss and increasing 18O/16O-ratio values in extracts with higher rates of change associated with higher ambient storage temperatures, probably due to evaporation (Thiem, Lüpke, & Seifert, 2004). The technique therefore does not readily lend itself to the analysis of ‘off the shelf’ retail samples unless the chilled storage history is well known.

The aims of this project were to develop reliable analytical methods that could establish the geographical origin of chicken based on its trace element ‘fingerprint’ and the natural abundance stable isotope ratios of the biological-elements hydrogen, carbon, nitrogen and oxygen and the heavy element strontium commonly found in all animal tissues. Here we present the findings from 384 poultry samples originating from Europe, China, Brazil, Chile, Thailand and Argentina.

Section snippets

Materials and methods

Three hundred and eighty four authentic poultry samples were obtained for this study. The vast majority of these samples (over 95%) were chicken samples, the remainder were turkey. The samples originated from seventeen different countries: Argentina (10 samples equivalent to 3% of total), Brazil (106, 27%), Chile (46, 12%), China (83, 22%), Thailand (37, 10%) and Europe (102, 26%). The 102 European samples originated from Austria (7), Czech Republic and Slovakia (1), Denmark (21), France (25),

Evaluation of poultry defatted dry mass (DDM) δ13C ‰ and δ15N ‰ isotopic measurements

The mean δ13C ‰ and δ15N ‰ values obtained from authentic European, Argentinean, Brazilian, Chilean, Thai and Chinese poultry DDM are summarised in Table 1. The Table also shows the sample standard deviation (σn-1) and the number of authentic samples measured (n). The difference in δ13C ‰ values between the South American (∼17.5‰) and European poultry (∼22.5‰) is relatively smaller than that observed for beef DDM (difference ∼ 10‰) (Heaton et al., 2008). This is probably due to a number of

Conclusions

This project has demonstrated that the stable isotopes of hydrogen in chicken meat change in accordance with hydrogen isotope ratios in surface waters around the globe. The findings support the theory that the global isotopic variation of hydrogen in drinking water is transferred into animal tissue and can be used to help establish an animal's geographic origin.

Furthermore, in some instances one variable was shown to be sufficient to discriminate geographical origins. For example, carbon stable

Acknowledgements

This research was financed by the UK Food Standards Agency as part of their Food Authenticity and Labelling Programme. The views expressed here are those of the authors and do not necessarily reflect the views of the UK Food Standards Agency.

The authors would also like to thank the following for their help in providing authentic poultry samples: The Port Health Authorities (UK), Bernard Matthews Ltd (Norwich, UK).

IQSTAP – Institute of Quality Standards and Testing Technology for Agricultural

References (32)

  • H. Craig

    Isotopic variations in meteoric waters

    Science

    (1961)
  • W. Dansgaard

    Stable isotopes in precipitation

    Tellus

    (1964)
  • EU 1169/2011

    Regulation (EU) No 1169/2011 of the European Parliament and of the council of 25 October 2011

    Off. J. Eur. Union

    (2011)
  • B.M. Franke et al.

    Indications for the applicability of element signature analysis for the determination of the geographic origin of dried beef and poultry meat

    European Food Research and Technology

    (2007)
  • B.M. Franke et al.

    Tracing the geographic origin of poultry meat and dried beef with oxygen and strontium isotope ratios

    European Food Research and Technology

    (2007)
  • K.A. Hobson

    Tracing origins and migration of wildlife using stable isotopes: a review

    Oecologia

    (1999)
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