Passata di pomodoro authenticity checks using δ18O analysis

Tomato puree (passata di pomodoro) represents a classic and emblematic Italian product around the world and is of considerable importance for the Italian economy. It has recently been estimated that 15% of industrial tomato comes from China in paste form (http://affaritaliani.libero.it/green/coldiretti_pomodoro_cina280311.html). For these reasons Italian law (Ministerial Decree of 23 September 2005) provides a very strict definition of ‘passata di pomodoro’ and establishes that the use of tomato concentrates over 12° degrees Brix and subsequent dilution to obtain ‘reconstituted passata’ is not permitted. Furthermore it indicates δ18O measurement in vegetal water (UNI ENV 12141 method) as the official method for detecting fraudulent dilution, but does not report any reference values for authentic passata. Trifirò et al. (2007) verified that passata effectively shows δ18O values significantly higher than products obtained by diluting tomato paste and proposed a minimum threshold value of -1.6‰ for authentic passata with Brix values between 7.5 and 10°. In this work we analysed authentic samples of passata, paste and diluted concentrate in order to check the validity of this threshold value and to establish a 18O limit value for passata produced by diluting products with a Brix value lower than 12°. A large number of samples of Italian ‘passata di pomodoro’ and paste from Italy, Greece, Turkey and China have been officially collected by the Italian Ministry of Agricultural, Food and Forestry Policy since 2009. Analysis of the δ18O of vegetal water was performed on these samples using an Isotope Ratio Mass Spectrometer (IRMS), interfaced with a CO2 equilibration system, according to the ENV 12141 method. The results essentially confirmed that -1.6‰ can be considered as the limit 18O value for authentic passata with a Brix of over 7.5°. Furthermore a δ18O of -2.5‰ can be considered as a limit value for passata coming from the dilution of products with a Brix level of less than 12°. All the diluted pastes showed δ18O values far below these limits. This research was funded by the Italian Ministry of Agricultural, Food and Forestry Policy.