IRMS (Isotope Ratio Mass Spectrometry) and ICP-MS (Inductively Coupled Plasma Mass Spectrometry) for the traceability and characterisation of premium products

There is an increasing demand for reliable analytical methods to verify the authenticity of the food we eat. First of all there is a growing enthusiasm for high quality food with a clear regional identity among consumers and scares such as BSE, chicken influenza and malpractice by some international food producers have added to public sensitivity regarding the validity of food origin labelling. In addition to heightened consumer awareness in the last few years, European Union policy on food has also been orientated towards safeguarding consumers. To achieve this scope the EU has on the one hand reinforced national control activities and on the other hand investigated new markers able to support food characterisation and geographical traceability, ensuring its authenticity. Along with elemental composition, the stable isotope ratios of bioelements such as hydrogen, carbon, oxygen, nitrogen and sulphur have been used for thirty years, both separately or jointly, in order to check the authenticity of different premium products. With regard to stable isotopes, this ability is based on isotopic fractionation occurring during physical and chemical processes, as well as along metabolic pathways. For this reason, the different isotopic ratios vary according to photosynthetic and nitrogen cycles, pedological characteristics of soils, agricultural practices and geographical origin. In contrast to stable isotope ratios, which mostly depend on climatic, hydrological or geographical conditions, elements are profoundly affected by soil geology and pedological characteristics, over and beyond ‘contamination’ during processing. Isotope ratio mass spectrometry and inductively coupled plasma mass spectrometry methods were developed to characterise and determine the authenticity of Italian and European extra virgin olive oils, olive oil squalene/squalane, Italian alpine PDO cheeses, Italian tomatoes and tomato derived products (juice, passata, paste). In particular, the d13C and d18O of Italian extra virgin olive oils made it possible to distinguish samples from North and South Italy, whereas different dD values, determined for the first time along with d18Obulk, were found in oils from the Italian Adriatic and Tyrrhenian coasts, improving the differentiation of samples from Central Italy. The isotopic composition of rainfall, along with the average temperature and humidity on the two coasts, can explain these differences in the oils. The combination of elemental composition and isotopic ratios analysis extended to olive oils collected at eight European sites, allowed good discrimination in relation to geographical provenance. ä13C, ä18O and äD were shown to be significantly correlated to geographical and climatic factors (e.g. latitude, distance from the coast, temperature), whereas elemental composition was related to the geological characteristics of the soil where the products were grown. Furthermore, d13C was shown to be a suitable marker for identification of squalene/squalane origin. By defining d13C threshold values of -27.4‰ for olive oil squalene/squalane, the addition of shark products can be detected starting from a minimum of 10%. The same analytical approaches, when applied to seven PDO Italian cheeses, made it possible to characterise them, and a statistical model built on the basis of the most significant analytical parameters obtained 94% discrimination of cheese type. Furthermore d13C, determined in casein or glycerol, allowed estimation of maize uptake in animal diet, making it possible to verify whether the levels established in the PDO production protocols were observed. d18O and d15N were instead shown to be very useful in differentiating mountain products. Stable isotope ratios and elemental composition determined in tomatoes and tomato products allowed good discrimination of samples from different Italian regions. Over 95% of the samples were correctly reclassified into the production site in crossvalidation, in spite of the food processing they had undergone. The δD and δ18Obulk values of tomatoes and derivatives were reported for the first time in the literature. To conclude the models developed for the specific commodities considered can be proposed as suitable tools for the detection of mislabelling and consumer protection, demonstrating that such analytical parameters can effectively contribute towards distinguishing the authenticity of commercial samples, becoming a tool for checking compliance with the law