Food Chemistry 145 (2014) 349–355

Contents lists available at ScienceDirect

Food Chemistryjournal homepage: www.elsevier.com/locate/foodchem

Precise determination of strontium isotope ratios by TIMS
to authenticate tomato geographical origin
P.R. Trincherini a,⇑, C. Bafﬁ b, P. Barbero a, E. Pizzoglio a, S. Spalla bab

LIMS (Laboratory for Isotope Mass Spectrometry), ‘‘L. Cobianchi’’, Piazza Martiri di Trarego 8, 28921 Verbania, Italy
Università Cattolica del S.Cuore, Istituto di Chimica Agraria e Ambientale, via Emilia Parmense, 84, 29122 Piacenza, Italya r t i c l e

i n f oArticle history:
Received 6 April 2013
Received in revised form 6 August 2013
Accepted 8 August 2013
Available online 26 August 2013
Keywords:
Strontium isotopic composition
TIMS
Food authentication
Fraud
Geographical origin
Tomatoa b s t r a c t
Thermal Ionisation Mass Spectrometry (TIMS) was applied to discriminate a total of 118 tomato samples(berries, ‘‘passata’’, tinned tomatoes, sauce, double and triple concentrate) coming from two different
countries. The TIMS technique gave signiﬁcantly different results for the 87Sr/86Sr ratios and d‰ values
between Chinese and Italian tomato samples, irrespective of the treatment type. This technique proved
to be a ‘‘robust’’ method, suitable for a precise discrimination of the two geographical origins. TIMS
was able, within the Italian samples, to discriminate different geographical production areas, by virtueof different 87Sr/86Sr ratios and d‰ values. This technique could be employed in the ﬁeld of food safety
and quality, as a proﬁtable tool for authenticating tomato geographical origin.
Ó 2013 Elsevier Ltd. All rights reserved.

1. Introduction
The authentication of the origin of food products, through a
precise determination of the different geographical origin, cananswer important questions concerning food safety, food quality
and consumer protection. In this regard the European Union (EU)
has issued some regulations concerning the protection of foodnames: protected designation of origin (PDO), protected geographical indication (PGI) and traditional specialities guaranteed (TSG)(Mout, 2004). The regulations now in force in the EU are 510/
2006 for PDO and 509/2006 for PGI; in 2002 an anti-fraud legislation (178/2002) was introduced; in 2006 the EU regulation 1898/
2006 was added. These indications are particularly important in
EU countries, where there has been a long tradition of associating
certain food products with particular regions (Luykx & van Ruth,
2008); at present, in EU countries, no legislation exists for governing and checking the import of plant foods, unlike the import offoods of animal origin which is ruled by EU Regulation 882/2004.
This fact, together with the different legislation in force in the ‘‘global’’ wider tomato trade market, allows illegal behaviour, such as
food fraud, which can damage both trade and human health. For
the future a globally-accepted legislation with severe monitoring
actions and penalties should be adopted; it should be based on⇑ Corresponding author. Tel.: +39 (0) 32352562.
E-mail address: pierre.trincherini@gmail.com (P.R. Trincherini).
0308-8146/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.foodchem.2013.08.030

shared ‘‘robust’’ methods, set up and validated in terms of internal
precision and external accuracy, independent of the ‘‘labelling’’.
The analytical approaches for determining the geographical origin of food products date from 1980s; they have been subdivided
into four groups: mass spectrometry techniques (IRMS, ICP-MS,
PTR-MS, GC–MS), spectroscopic techniques (NMR, IR, ﬂuorescenceand atomic spectroscopy), separation techniques (HPLC, GC, CE)
and other techniques, including DNA technology and sensor analysis (Luykx & van Ruth, 2008). The most employed approach forestablishing the geographical origin of food compounds seems toconsist in a combination of the above methods; nevertheless, fora single food, fresh or processed, in a single laboratory, the results
obtained by a validated analytical method could proﬁtably support
the legislator’s decisions.
As far as tomato authenticity is concerned, numerous studies
have been developed in recent years (Arvanitoyannis & Vaitsi,2007). Magnetic Resonance Imaging (MRI) spectroscopy has
allowed the distinction between PGI fresh cherry tomatoes andnon-PGI ones (Sequi, Dell’ Abate, & Valentini, 2007). 1H NMR(nuclear magnetic resonance) spectroscopy, in combination withmultivariate analysis has differentiated the metabolite content ofChinese and Italian tomato pastes (Consonni, Cagliani, Stocchero,& Porretta, 2009; Consonni, Cagliani, Stocchero, & Porretta, 2010).
Inductively coupled plasma mass spectrometry (ICP-MS) in combination with linear discriminant analysis (LDA), soft independent
modelling of class analogy (SIMCA) and K-nearest neighbours(KNN), have been employed to discriminate different geographical

350

P.R. Trincherini et al. / Food Chemistry 145 (2014) 349–355

zones for fresh tomatoes and triple concentrated tomato paste (LoFeudo, Naccarato, Sindona, & Tagarelli, 2010). Until now, no study
has been published concerning the discrimination of the geographical origin for tomato with the use of thermal ionisation mass
spectrometry (TIMS).
This technique has been successfully employed in hydrology(Chaudhuri, 1978), in geochemistry and cosmochemistry (Dickin,
1995; Faure, 1986; Huchon, Taylor, & Klaus, 2001), in Anthropology (Evans, Chenery, & Montgomery, 2012; Latkoczy, Prohaska,
Watkins, Stingeder, & Teschler Nicola, 2001), for forensic purposes(Beard & Johnson, 2000; Rummel, Hoelzl, & Horn, 2007) and it has
been applied in the food ﬁeld to authenticate the origin of wines,
vegetables, dairy products and beef (Barbaste, Robinson, Guilfoyle,Medina, & Lobinski, 2002; Horn, Schaaf, Holbach, Holzi, & Eschnauer,
1993; Rossmann et al., 2000; Rummel et al., 2012; Swoboda et al.,2008). It takes advantage of the principle according to which,during growth, plants absorb nutrients from the soil without any
interference, such as isotopic fractionation (Stewart, Capo, &Chadwich, 1998). Good correlations were observed between theconcentration proﬁle of heavy metals in plant foods and in the soil
where they were grown, which were even better for fresh foods
than those derived from metabolic processes (Fortunato et al.,2004).
In nature Strontium is present with four stable isotopes: 88Sr,
87Sr, 86Sr and 84Sr, where the isotope composition varies according
to the b-decay of 87Rb, which turns into 87Sr with a half-life decay
time (T1/2) of 4.7  1010 years. The Rb–Sr combination generates
different 87Sr/86Sr isotopic ratios which, reﬂecting only the variations in the amount of radiogenic 87Sr present in the sample, depend on the age and on the pedological characteristics of soils
where they naturally occur, namely their geographical origin. The
net result is that the strontium isotopic composition of a sample
yields information about provenance or geological interaction,
unobscured by local temperature variations or internal biologicalprocesses (Capo, Stewart, & Chadwick, 1998). These results wereconﬁrmed by data of Sr isotopic ratios carried out on a high number of European mineral waters, where the different 87Sr/86Sr ratios
observed (range 0.7035–0.7777) were signiﬁcantly affected by different rock types, after being permeated by waters (Voerkelius
et al., 2010).
The possibility to discriminate different geographical origins
within small ranges of variation of the 87Sr/86Sr isotope ratios, requires high precision of the measurement and this can be reachedby the thermal ionisation mass spectrometry (TIMS) technique. For
food traceability, sector ﬁeld mass spectrometry with plasma
source (SF-ICP-MS), both with single and multiple collectors(MC-SF-ICP), was used for solid samples, while SF-ICP-MS andthe TIMS technique were employed for water samples. TIMS isrecognised as the most precise technique, although it is time consuming, because it lacks isobaric interference of a molecular nature
which forms during the ionisation processes in the spectrometerswith plasma sources; moreover TIMS is very suitable for dealing
with an investigation based both on the discrimination between
isotope ratio values 60.1% and on an internal precision of the measurement better than 0.005%. In all isotope techniques, before measurement, it is essential to separate Sr from Rb, in order toeliminate the isobaric interference caused by 87Rb which is always
present, although with variable concentrations, in samples fromgeological environments, and therefore also in the samples of foodchains closely bound to them. The tomato (Licopersicum esculentum) is a plant belonging to the family of the Solanacee. Botanically,
it is an ovary, with seeds of a ﬂowering plant; therefore it is a fruit
or, more precisely, a berry with a typical red colour. Tomatoes canhave beneﬁcial effects on human health, due to the presence ofantioxidants such as carotenoids (lycopene and b-carotene) andpolyphenols (ﬂavonoids and hydroxyl cinnamic acids). About
1700 tomato varieties are registered in the world, but only 100of them are responsible for 70% of total world production. In Italy
300 tomato varieties are registered but only 60 of them are usedevery day (http://www.zipmec.eu/en/Vegetables-production-andprocessing-trade/tomatoes-history-production-trade.html). World
production of fresh tomatoes in 2012 was 33 million tons (M t)(World Production Estimate of Tomato Processing – WPTC.,
2012), a quarter of which is devoted to industrial processing. Italy(4.5 M t) is the leading producer among the Members in Mediterranean Area (AMITOM) (13.8 M t) and the second producer in theworld, preceded by California (11.7 M t). China, with 3.2 M t, isthe third world producer, having acquired this position in only
15 years (World Processing Tomato Council, WTO, 2012). As far
as exports of tomato are concerned, China is the world leader, followed by Italy. The biggest market for Chinese exports is the EU 27
area. China started to export in 1995, ﬁrstly, to the neighbouring
nations of the Far East (Japan, Philippines, Korea), then, in the subsequent 15 years, to EU countries (Italy, Germany, UK) and Russia.
After 2004 Chinese producers opened up new markets for theirproducts, especially in North and West Africa. China has also become a transformer of tomato by virtue of new installations sitednear Gansu and in Mongolia and it is the only nation in the world
not subjected to any law concerning tomato cultivation so it can
produce GMO tomatoes too. As regards tomato processing, in Italy,
in 2012, the Regions of Apulia and Emilia-Romagna have devoted
34% and 33% of the national utilised agricultural area (UAA) for
tomato cultivation, representing 37% and 31%, respectively, of thetotal Italian production. China, is the main supplier (52.9% of thetotal) of semi-manufactured tomatoes for Italy; in these last
10 years imports of concentrated tomatoes from China have increased fourfold (+272%). Tinplate packings of tomato concentrate,of over 200 kg, are unloaded from Chinese ships; this product isprocessed again and packed as an Italian product; this is possible
because, by virtue of the legislation in force, the indication of theorigin of the cultivated product is not compulsory on the containers for sale, the mark of packaging being enough. The Chinese
tomato product is characterised by a very competitive price but,lacking in most of the qualitative and organoleptic characteristicsof the Italian tomato products, it is often used to blend the Italianproduct; in this way it supplements the national supply. The risk isthat often this mixed product can be marketed with the wording‘‘made in Italy’’.
The aim of this study was to verify the suitability of TIMS as a‘‘robust’’ technique for the authentication of the geographical origin of processed or fresh tomato samples coming from China and
Italy, through a discrimination based on a precise determinationof the 87Sr/86Sr ratios. This may allow us to build up isotopic clusters, relative to Chinese and Italian tomato products, irrespective ofthe type, e.g. fresh or processed, so as to enable a sure geographicalassessment of the place of origin for unknown samples whether
Chinese or Italian.

2. Experimental
2.1. Samples
Fig. 1 shows the geographical distribution of the total 118 tomato samples, listed below following a chronological sampling timeorder:
 40 samples from the Province of Piacenza, Region of EmiliaRomagna, north Italy: berries, double and triple concentrated
tomato paste, in tins; years 2006–2008.

P.R. Trincherini et al. / Food Chemistry 145 (2014) 349–355

351

ItalianRegions:
EmiliaRomagna (North), Campania
and Apulia (South)

Chinese Provinces: Xingjiang (NW)and Hubei (Centre-East)
Fig. 1. Provenance areas of tomato samples. Left: the Emilia-Romagna Region (north Italy), the Apulia and Campania Regions (south Italy). Right: the Xinjiang (NW) and the
Hubei (Central-East) Provinces of China.

 30 selected samples from the Provinces of Piacenza, Parma andFerrara; Emilia-Romagna Region, north Italy: samples of berries(1–2 kg of different cultivars) and ‘‘passata’’ (0.5 kg) in glass
bottles; year 2010.
 30 samples from China: double and triple concentrated paste
and tomato sauce of 70–200 g in size (Hubei Province) and of
3.0 kg in size (Xinjiang Province), in tinplate packings; year2011.
 12 samples from the Region of Apulia, southern Italy: mini-tinsof tomatoes in 100 g size tins; year 2011.
 6 ‘‘blind’’ samples of unknown origin: ‘‘passata’’ and tinned
tomatoes (0.5–4.0 kg), in glass bottles and tin cans; year 2011.

(Sigma–Aldrich, St. Louis, MA, USA) puriﬁed by a ping-pong subboiling Ó Teﬂon distillation system, were used for sample dissolution procedures. Glassware was rinsed by overnight immersion in asolution of HNO3 (10% m/v), followed by rinsing with deionised
water. The SRM 987 (SrCO3 isotopic) from the National Standards
and Technology (NIST) (Gaithersburg, MD, USA) was used forexternal precision measurement (RESD) and method validation.
Except for freeze-drying and dissolution, all the other lab operations were carried out under Class 100 clean conditions (Aquaria,
MI, I). FEP (ﬂuorinated ethylene propylene) containers were used
for the storage and treatment of the samples, according to awell-documented and certiﬁed procedure (Trincherini et al., 2003).

All the samples were collected by the staff of a private processing tomato ﬁrm (Mutti S.p.A., Montechiarugolo, Parma, I) and by
the personnel of the Institute of Agricultural and Environmental
Chemistry (IAEC, Catholic University, Piacenza, I) according to thesampling times listed above. In order to guarantee the maximum
correspondence between ‘‘passata’’ and berries, for the set of 30 tomato samples selected from north Italy, a particular sampling
scheme with georeferenced samples was adopted. The other samples were obtained directly or through commercial trade channels,
making sure they were representative of the geographical area of
provenance. After preliminary treatments such as quartering,
blending and freeze-drying, carried out in the IAEC laboratory,
the samples were sent to the Laboratory for Isotope Mass Spectrometry (LIMS; Verbania, I) for dissolution, chemical pre-treatment and isotope measurements.

2.3. Instrumentation

2.2. Materials: reagents and standard solutions
HNO3 (Traceselect), analytical grade reagents (H2O2) andhigh-purity deionised water, Milli-Q (18.2 MX) from Millipore

The instrumentation for sample preparation consisted in afreeze-dryer (mod. Mini Fast 680, Edwards, Norfolk, UK) for lyophilisation, in a closed microwave oven (MILESTONE, Montoe, CT,
USA) or in a simple digestion under controlled atmosphere forchemical dissolution, in an atomic absorption spectrometer(VARIAN Mod220; Varian Australia Ltd, Mulgrave 3170, Victoria,
Australia) for the determination of Sr and Rb concentrations in digested samples, and in a Sr-resin 50–100 lm from EiChrom Europe(Triskem, Bruz, F) for Sr–Rb separation. The instrumentation forisotope analysis consisted in a Finnigan 262 VMC mass spectrometer (Finnigan, Thermo Scientiﬁc GmbH, Bremen, D), able to focus
the following masses: 84Sr, 85Rb, 86Sr, 87Sr and 88Sr, and equippedwith 5 Faraday cups placed in a variable multicollector, with extensive optical geometry, but corresponding to a system that has aconventional geometry, with a 64 cm deﬂection radius.
The measurements were carried out on the ‘‘zone reﬁned’’rhenium (Re) ﬁlaments (H. Cross Co., Moonachie, NJ, USA). An
advanced software for data acquisition was installed by Spectromat

352

P.R. Trincherini et al. / Food Chemistry 145 (2014) 349–355

GmbH, Bremen, D. Parameters such as mass calibration and gain
calibration, were performed for the multicollector daily. The instrument can accept a block of thirteen samples with two reference isotopic standards (SRM NIST 987) as continuous accuracy control.
Together with over 100 tomato samples, 35 samples of isotopic
standard were measured with a ﬁnal value of 0.71031 ± 0.00003,
equivalent to an internal precision better than 40 ppm and an
external precision comparable with the certiﬁed value.

In Fig. 2a the value of the 87Sr/86Sr isotopic ratio is assumed tobe equal to 0.7100, for the total absence of Rb; increasing amountsof Rb (expressed as the % Rb/Sr ratio) can strongly modify the measurement of the 87Sr/86Sr isotopic ratio. By extrapolation of thedashed area the precision and the acceptable Rb/Sr percentage values can be better observed, with no mathematical corrections as inFig. 2b, necessary for the present investigation.

3.2. Isotopic ratio measurements
3. Measurements
3.1. Sample pre-treatment
In the IAEC lab all samples, except the liquid ones, after quartering, were submitted to a mixing procedure before freeze-drying,
carried out for two days at T = 40 °C, with the use a freeze-dryer.
Then samples were ground by using agate mortar and pestles toobtain a ﬁneness of 1–2 mm. Subsequently they were sent to LIMS
lab, in polyethylene bottles, for analysis.
For digestion, a 250–300 mg of freeze-dried sample was dissolved by using both a microwave assisted digester and chemical
mineralisation working under a controlled atmosphere. In bothcases, 2–3 mL of HNO3 (Traceselect) and, sometimes a few dropsof ultrapure H2O2 were added as digestion reagents. As far as thedissolution completeness and the results of the determination of
the isotopic ratios are concerned, no difference was observed between the above two methods, except for a shorter time for the assisted digestion. After evaporation to dryness, the residue wasdissolved again in 10 mL of 8 M HNO3 and the solution thus obtained was transferred to a Sr-resin column, where Sr was ﬁxed,
then eluted with 0.05 M HNO3 and ﬁnally eliminated as a leachate.
The most suitable conditions for Rb/Sr separation had previously
been established by measuring, by AAS, the concentrations of Srand Rb in an initial series of 40 digested tomato samples. The Rb/
Sr concentration ratio showed values close to 1 for 63% of the samples, between 0.5 and 1 for 15% of the samples and <4 for theremaining 22% of the samples; Sr concentration values ranged
from a minimum of 1 ppm to a maximum of 12 ppm, with an average value of 5.30 ppm. The separation procedure was optimisedusing the speciﬁc Sr-resin described above, following a separation
procedure optimised to a well-known and documented method(Fortunato et al., 2004; Swoboda et al., 2008; Trincherini et al.,2003). At ﬁrst the resin was conditioned with HNO3 (about 1% w/w) for at least 12 h, during which the supernatant HNO3 was replaced at least twice. Once employed, the resin can be utilised
again, subject to an accurate series of washings with HNO3 (about
1% w/w) and rinsing with ultrapure and redistilled water. Sometests carried out on the recycled resin using the certiﬁed standard
SRM 987 served to ascertain the complete absence of the Sr previously employed. The measurement of Sr and Rb concentrations by
AAS was necessary to ﬁx the aliquot of the sample to be loaded on
the resin in conformity with EiChrom Recommendations(EiChrom; Horwitz, Chiarizia, & Dietz, 1992), according to which
the resin should be charged with 10–20% of the maximum capacity, i.e. about 10 mg mL1. The volume of the sample was reduced
to 5 mL and the washing of the resin was done with 2–3 mL HNO3
6–7 mol L1. At the end the eluate containing Sr was submitted todry evaporation, recovered with 50 lL of HNO3 1% and, later on,
reduced at the time of the deposition on the ﬁlament. Following
experimental optimisation of volumes and concentrations, theseparation of Sr–Rb can achieve very good results but hardly ever
100%. In particular, in some samples where the Rb/Sr ratio is equal
to 1.5–2.0 or more, the eluate can include signiﬁcant traces of Rb.
This element can strongly affect the measurement of the isotopic
ratio inducing a positive drift, as can be seen in Figs. 2a and 2b.

The mass spectrometer TIMS (Finnigan 262 VMC) was equippedwith a multicollector system able to focus the following masses:
84
Sr, 85Rb, 86Sr, 87Sr and 88Sr. Since mass 85 is present only in the
Rb and not in Sr isotopic composition, it can be monitored continuously without any interference and the 87Rb value can be deduced
from the 85Rb value since the 85Rb/87Rb ratio is about 3. Inside thespectrometer, the heating program for ﬁlaments of emission andevaporation (the sample is deposited on the latter) allows us to‘‘burn’’ Rb traces and to check the total absence of signal at mass
85. Only at this point is it possible to begin the data acquisition
concerning isotopic 87Sr/86Sr ratio values. The long-lasting stabilityof the signal produced by ions emitted by ﬁlaments is responsible
for the high precision of the measurement obtained by this technique where, once the best separation has been set up, the measurement process is no longer subject to any interference. The
software of the instrument foresees a series of fundamental calibrations, among which, in particular, the detector scan of each Faraday cup and the vision of their alignment (Fig. 3). The stability ofthe peak shape, especially the top one, differentiates the measure
carried out by use of isotopic ratios by TIMS from that obtainedby any other instrument, ICP-source mass spectrometers included.
Rosner (2010) accurately analyses the problems involved in themeasurement of the isotopic ratio 87Sr/86Sr when an ICP-source
is used. They are very complex and difﬁcult to solve when a quadrupole sector is used, but partially remediable when a double
focussing (DF) mass spectrometer equipped with a multicollector(MC) is used. Also in this instance, however, the presence of noneliminable ions (Kr+), partially non-eliminable ions (Rb+) and ofmolecular interferent ions, originated from the matrix composition, requires mathematical corrections which are not always andnot necessarily univocal. The certiﬁed standard SRM 987 (NIST)
was used to ensure quality both as an internal standard and as acheck for instrumental functionality, with the criterion of two
standards at the least for every ten samples. The series of results(n = 36) gave a value of the internal precision, the relative internal(a)Fig. 2a. Changes in the 87Sr/86Sr isotopic ratio according to the increasing amountsof Rb added.

P.R. Trincherini et al. / Food Chemistry 145 (2014) 349–355

353

(b)

Fig. 2b. The smallest dark area shows the precision range required and the relative maximum allowable percentage of Rb according to the precision needed.

Fig. 3. Data concerning the 87Sr/86Sr ratio and d‰ in tomato samples from Italy andChina; d‰ = 0 is for the SRM 987 standard certiﬁed sample.

standard deviation (RISD) 6 40 ppm and of the accuracy, the relative external standard deviation (RESD), about 20 ppm. All samples
were analysed in duplicate and the results gave a value of reproducibility <40 ppm. The d‰ of the isotopic ratio 87Sr/86Sr was
calculated by the algorithm:

d87 Srð‰Þ ¼ ð87 Sr=86 Sranalysed =87 Sr=86 Srstandard  1Þ  1000

Fig. 4. Position of values of 87Sr/86Sr and d‰ ‘‘blind’’ tomato samples respect toItalian and Chinese samples.

ð1Þ

where SRM 987 is the reference standard.
The statistical analysis was performed with the IBM SPSSÓ
vers.19.0 software package. All data were tested ﬁrstly for normality (Shapiro & Wilk, 1965), then underwent both the Levene’s testfor equality of variances (Levene, 1960) and the ANOVA 1-way andthe t-test of independent samples (Clewer & Scarisbrick, 2001).
4. Results and discussion
In preliminary trials a series of 40 tomato samples (berries, double and triple concentrate) from the Province of Piacenza (north
Italy) were analysed in order to set up the method in terms of
the optimisation of the conditions for the analysis (amount, contact time, reading time, etc.). Subsequently a series of 30 selected
samples (berries and ‘‘passata’’) from north Italy and 30 samples

Fig. 5. Italian sample distribution according to different areas of production: d‰ vs87
Sr/86Sr ratio.

354

P.R. Trincherini et al. / Food Chemistry 145 (2014) 349–355

Table 1
Mean values of the 87Sr/86Sr ratio and d‰ in tomato samples; statistical results (t-test of the independent samples) for mean comparisons.
Provenance of samples

87

Sr/86Srd‰StatisticalcomparisonsNorth-Italy
South-Italy
China‘‘Blind’’ samples
Italy
China

0.70817 ± 0.00039
0.70793 ± 0.00022
0.71051 ± 0.00033
0.70871 ± 0.00022
0.70810 ± 0.00036
0.71051 ± 0.00033

2.06 ± 0.548
2.39 ± 0.303+1.24 ± 0460
1.30 ± 0.303
2.15 ± 0.303+1.24 ± 0460

n.s.
n.s.

**
**
**

n.s.
n.s.

**

**
**
**

**

n.s. = not signiﬁcantly different.
**
Statistical signiﬁcance (t independent test) with P < 0.01.

(sauces, double and triple concentrated tomato paste) from China(Xingiang and Hubei Provinces) were analysed, together with thecertiﬁed standard SRM 987, in order to verify a real discriminantcapacity of the proposed technique. The 87Sr/86Sr ratio mean values
were 0.70817 ± 0.00039 for the samples from north Italy and0.71051 ± 0.00033 for the samples from China; d‰ mean values
were 2.06 ± 0.548 for the northern Italian samples and1.24 ± 0.460 for the Chinese samples. The t-test of the independent
samples highlighted signiﬁcant differences (P < 0.01) between
mean values of samples from the two populations (north Italy
and China).
A second series of 12 mini-tins of tomato samples from southern Italy, subsequently analysed, gave mean values of
0.70793 ± 0.00022 for 87Sr/86Sr ratio and of 2.39 ± 0.303 for d‰.
The t-test of the independent samples conﬁrmed the presence ofsigniﬁcant differences (P < 0.01) between mean values of samples
from south Italy and China and no difference between southern anorthern Italian tomato samples.
Fig. 4 shows data of the 87Sr/86Sr ratio and the d‰ values for
Italian and Chinese tomato samples. The former constitutes aunique homogeneous population with mean values of
0.70810 ± 0.00036 for the 87Sr/86Sr ratio and of 2.15 ± 0.303 ford‰, below the zero line d‰ = 0 of certiﬁed standard SRM 987.
Mean values for the 87Sr/86Sr ratio and d‰ of the two populations
resulted signiﬁcantly (P < 0.01) different with the t-independent
test.
Lastly 6 ‘‘blind’’ samples were analysed; the results gave meanvalues of 0.70871 ± 0.00022 for the 87Sr/86Sr ratio and of
1.30 ± 0.303 for d‰. Fig. 5 shows the positions they occupy inthe plot d‰ vs 87Sr/86Sr ratio, with respect to the Italian andChinese samples. The t test highlighted that they were signiﬁcantly(P < 0.01) different from the Chinese samples but did not differ
from the Italian samples (see Table 1). The ﬁrm which suppliedthe ‘‘blind’’ samples afterwards told us their provenance: southern
Italy (three from the Apulia Region and three from the Campania
Region).
A series of ten samples, ﬁve Italian and ﬁve Chinese, was analysed later in time, in order to investigate the total reproducibilityof the method, including both the sample preparation and themass-spectrometric measurement. For nine samples the reproducibility was 660 ppm and for one sample was equal to 91 ppm;
these values guarantee the boundaries of the relative clusters
and, according to this, the certain discrimination between thetwo geographical origins. A one-way ANOVA carried out on all of
the Italian samples revealed signiﬁcant differences (P < 0.01) concerning the mean values of the 87Sr/86Sr ratio and d‰ values, withlower values observed for samples from organic hydromorphic
soils of the youngest geological age, intermediate values for samples from poorly evolved soils of intermediate geological age andhigher values for samples from more ancient soils developed onolder rocks (see Fig. 5). In literature there is little research on thecorrelation between the Sr isotope ratio and soil geographicalorigin, compared to the numerous studies on mineral waters(Voerkelius et al., 2010).
There are rare cases where only the measurement of the isotopic ratio 87Sr/86Sr is not sufﬁcient to discriminate two geographicalareas showing similar geological features; consequently, it isnecessary to add at least one other technique, for example the multielemental analysis (Bong et al. 2012). Here the main aim was tosupply a sure method to discriminate two distant geographical origins (Italy and China), which could be used for anti-fraud purposes.
For this aim our study has taken into account more than one
hundred of tomato samples of different types and the resultsunambiguously prove that this aim was achieved. The precision
and accuracy of the employed method were able to differentiate,
within Italian tomato samples, those coming from soils with different geological ages.
5. Conclusions
For the aim of this work TIMS proved to be a ‘‘robust’’ analyticaltechnique, in that it allowed a precise geographical discriminationof the origin of tomato products, both fresh and processed, comingfrom Italy and China. Within the Italian samples due to the high precision and accuracy of this technique, the method was able to discriminate tomato products from soils of different geological ages.
This method could be used as a proﬁtable tool to authenticate
tomato origin of both fresh and processed samples coming from
Italy and China, because it is independent from the industrial treatment that tomatoes undergo and depends only on the cultivationsoil age. As a consequence the two distinct ‘‘clusters’’ of population
built up in this study could be useful for identifying the certain
geographical origin of tomato products in case of doubt concerning
trade declaration about the provenance. This could be important tocontrast the growing illegal imports of tomato products from countries where the strict EU legislation is not in force. If, on the one
hand, this method ﬁghts trade frauds, on the other hand, its importance is particularly relevant for the defence of certiﬁed foods (PGI
and PDO) and for the protection and safety of consumer health. A
further development could consist in an increase of the databasethrough the introduction of new samples both from selected areas
and, later on, from geographical areas with few food frauds.
Acknowledgements
The authors thank Dr. Francesco Mutti and his staff (Mutti
S.p.A., Montechiarugolo, PR, I) for the collaboration in supplying
tomato samples and for the ﬁnancial support.
References
Arvanitoyannis, I. S., & Vaitsi, O. B. (2007). A review on tomato authenticity: Quality
control methods in conjunction with multivariate analysis (Chemometrics).
Critical Reviews in Food Science and Nutrition, 47, 675–699.

P.R. Trincherini et al. / Food Chemistry 145 (2014) 349–355
Barbaste, M., Robinson, K., Guilfoyle, S., Medina, B., & Lobinski, R. (2002). Precise
determination of the strontium isotope ratios in wine by inductively coupledplasma sector ﬁeld multicollector mass spectrometry (ICP-SF-MC-MS). Journalof Analytical Atomic Spectrometry, 17, 135–137.
Beard, B. L., & Johnson, C. M. (2000). Strontium isotope composition of skeletalmaterial can determine the birth place and geographic mobility of humans andanimals. Journal of Forensic Sciences, 45(5), 1049–1061.
Bong, Y. S., Shin, W. J., Gautam, M. K., Jeong, Y. J., Lee, A. R., Jang, C. S., et al. (2012).
Determining the geographical origin of Chinese cabbages using multielement
composition and strontium isotope ratio analyses. Food Chemistry, 135,
2666–2674.
Capo, R. C., Stewart, B. W., & Chadwick, O. A. (1998). Strontium isotopes as tracers of
ecosystem processes: Theory and methods. Geoderma, 82, 197–225.
Chaudhuri, S. (1978). Strontium isotopic composition of several oilﬁeld brines from
Kansas and Colorado. Geochimica et Cosmochimica Acta, 42, 329–331.
Clewer, A. G., & Scarisbrick, D. H. (2001). Practical statistics and experimental designfor plant and crop science. Chichester, UK: John Wiley and Sons Inc.. 332 pp..
Commission Regulation (EC) No. 1898/2006 of 14 December 2006 laying down
detailed rules of implementation of Council Regulation (EC) No. 510/2006 on
the protection of geographical indications and designations of origin for
agricultural products and foodstuffs (OJ L369; 23.12.2006).
Consonni, R., Cagliani, L. R., Stocchero, M., & Porretta, S. (2009). Triple concentrated
tomato paste: Discrimination between Italian and Chinese products. Journal of
Agricultural and Food Chemistry, 57, 4506–4513.
Consonni, R., Cagliani, L. R., Stocchero, M., & Porretta, S. (2010). Evaluation of the
production year in Italian and Chinese tomato paste for geographicaldetermination using O2PLS models. Journal of Agricultural and Food Chemistry,
58, 7520–7525.
Council Regulation (EC) No. 509/2006 of 20 March 2006 on agricultural products
and foodstuffs as traditional specialities guaranteed (OJ L 93; 31.3.2006).
Council Regulation (EC) No. 510/2006 of 20 March 2006 on the protection ofgeographical origin (OJ L 93; 31.3. 2006).
Dickin, A. P. (1995). In A. P. Dickin (Ed.), Radiogenic isotope geology. Cambridge
University Press.
Eichrom. <http://www.eichrom.com/products/info/sr-resin.aspx>.
Evans, J. A., Chenery, C. A., & Montgomery, J. (2012). A summary of strontium andoxygen isotope variation in archaeological human tooth enamel excavated fromBritain. Journal of Analytical Atomic Spectrometry, 27(5), 754–764.
Faure, G. (1986). Principles of isotope geology 2nd ed.. New York: John Wiley.
Fortunato, G., Mumic, K., Wunderli, S., Pillonel, L., Bosset, J. O., & Gremaud, G. (2004).
Application of strontium isotope ratios measured by MC-ICP-MS for foodauthentication. Journal of Analytical Atomic Spectrometry, 19, 227–233.
Horn, P., Schaaf, P., Holbach, B., Holzi, S., & Eschnauer, H. (1993). 87Sr/86Sr from rockand soil into vine and wine. Zeitschrift für Lebensmittel–Untersuchung und –Forschung, 196, 407–409.
Horwitz, E. P., Chiarizia, R., & Dietz, M. L. (1992). Solvent Extraction and Ion Exchange,
10(2), 313–336.
Huchon, P., Taylor, B., & Klaus, A. (2001). In P. Huchon, B. Taylor, & A. Klaus (Eds.),
Proceedings of the ocean drilling program – Scientiﬁc results (pp. 1–36). College
Station, TX: Ocean Drilling Program. Leg 180.
Latkoczy, C., Prohaska, T., Watkins, M., Stingeder, G., & Teschler Nicola, M. (2001).
Strontium isotope ratio determination after on-line matrix separation bycoupling ion chromatography (HPIC) to an inductively coupled plasma sector
ﬁeld mass spectrometer (SF-ICP-MS). Journal of Analytical Atomic Spectrometry,
16, 806–811.
Levene, H. (1960). Robust tests for equality of variances. In I. Olkin & H. Hotelling,
et al. (Eds.), Contribution to probability and statistics (pp. 278–292). New York:
Stanford University Press.

355

Lo Feudo, G., Naccarato, A., Sindona, G., & Tagarelli, A. (2010). Investigating theorigin of tomatoes and triple concentrated tomato pastes through multielement
determination by inductively coupled plasma mass spectrometry and statisticalanalysis. Journal of Agricultural and Food Chemistry, 58, 3801–3807.
Luykx, D. M. A. M., & van Ruth, S. M. (2008). An overview of analytical methods fordetermining the geographical origin of food products. Food Chemistry, 107,
897–911.
Mout, L. (2004). Geographical indicated products in The Netherlands. PhD thesis,
Wageningen, The Netherlands.
Regulation (EC) No. 178/2002 of the European Parliament and of the Council of 28
January 2002 laying down the general principles and requirements of food law,establishing the European Food Safety Authority and laying down procedures inmatters of food safety (OJ L31; 1.2.2002).
Regulation (EC) No. 882/2004 of the European Parliament and of the Council of 29
April 2004 on ofﬁcial controls performed to ensure the veriﬁcation ofcompliance with feed and food law, animal health and animal welfare rules(OJ L165; 30.4.2004).
Rosner, M. (2010). Geochemical and instrumental fundamentals for accurate andprecise strontium isotope data of food samples: Comment on ‘‘Determination of
the strontium isotope ratio by ICP-MS ginseng as a tracer of regional origin’’(Choi et al., 2008). Food Chemistry, 121, 918–921.
Rossmann, A., Haberhauer, G., Holzl, G., Horn, P., Pichlmayer, F., & Voerkelius, S.
(2000). The potential of multielement stable isotope analysis for regional origin
assignment of butter. European Food Research and Technology, 211(1), 32–40.
Rummel, S., Dekant, C. H., Hoelzl, S., Kelly, S. D., Baxter, M., Marighito, N., et al.
(2012). Sr isotope measurements in beef – Analytical challenge and ﬁrst results.
Analytical and Bioanalytical Chemistry, 402, 2837–2848.
Rummel, S., Hoelzl, S., & Horn, P. (2007). Biologische spurenkunde, Band I:
Kriminalbiologie. Berlin, Heidelberg: Springer. 381–407.
Sequi, P., Dell’ Abate, M. T., & Valentini, M. (2007). Identiﬁcation of cherry tomatoes
growth origin by means of magnetic resonance imaging. Journal of the Science ofFood and Agriculture, 87, 127–132.
Shapiro, S. S., & Wilk, M. B. (1965). Analysis of variance tests for normality(complete sample). Biometrika, 52, 591–611.
Stewart, B. W., Capo, R. C., & Chadwich, O. A. (1998). Quantitative strontium isotope
models for weathering, pedogenesis and biogeochemical cycling. Geoderma, 82,
173–195.
Swoboda, S., Brunner, M., Boulyga, S. F., Galler, P., Horacek, M., & Prohaska, T. (2008).
Identiﬁcation of Marchfeld asparagus using Sr isotope ratio measurements by
MC-ICP-MS. Analytical and Bioanalytical Chemistry, 390(2), 487–494.
Trincherini, P. R., Serra, F., Pivato, M., Tanet, G., Van Haecke, F., Raniero, F. andGuillou, C. (2003). The characterization of the geographical origin of green
coffee: A multi-isotopic approach. In: ISI: 2nd international symposium on
isotopomers, Stresa, Italy.
Voerkelius, S., Lorenz, G. D., Rummel, S., Quétel, C. R., Heiss, G., Baxter, M., et al.
(2010). Strontium isotopic signatures of natural mineral waters, the reference
to a simple geological map and its potential for authentication of food. Food
Chemistry, 118(4), 933–940.
WPTC. (2012). ANICAV (Associazione Nazionale Industriali Conserve Alimentari
Vegetali), Stime mondiali di prodotto trasformato. Newsletter 184/2012, Napoli,
Italy.

Websitehttp://www.zipmec.eu/en/Vegetables-production-and-processing-trade/tomatoeshistory-production-trade.html.