BÁO CÁO KHOA HỌC VỀ DẦU BÍ ĐỎ

Food Chemistry 136 (2013) 1533–1542 Contents lists available at SciVerse ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem Suitability of elemental fingerprinting for assessing the geographic origin of pumpkin (Cucurbita pepo var styriaca) seed oil Donata Bandoniene ⇑, Daniela Zettl, Thomas Meisel, Marija Maneiko Montanuniversitaet Leoben, General and Analytical Chemistry, Franz-Josef-Straße 18, Leoben 8700, Austria a r t i c l e i n f o Article history: Available online 29 June 2012 Keywords: Rare earth element analysis Trace elements Geographical origin Plant oil Multivariate statistics ICP-MS a b s t r a c t An analytical method was developed and validated for the classification of the geographical origin of pumpkin seeds and oil from Austria, China and Russia The distribution of element traces in pumpkin seed and pumpkin seed oils in relation to the geographical origin of soils of several agricultural farms in Austria was studied in detail Samples from several geographic origins were taken from parts of the pumpkin, pumpkin flesh, seeds, the oil extracted from the seeds and the oil-extraction cake as well as the topsoil on which the plants were grown Plants from different geographical origin show variations of the elemental patterns that are significantly large, reproducible over the years and ripeness period and show no significant influence of oil production procedure, to allow to a discrimination of geographical origin A successful differentiation of oils from different regions in Austria, China and Russia classified with multivariate data analysis is demonstrated Ó 2012 Elsevier Ltd All rights reserved Introduction The authenticity and origin of pumpkin seed oil is of important from the standpoint of both commercial value and health aspects (Awad, von Höltz, Cone, Fink, & Chen, 1998; Fruhwirth, Wenzl, El-Toukhy, Wagner, & Hermetter, 2003; Murkovic, Hillebrand, Winkler, & Pfannhauser, 1996) Inimitable aroma of Styrian pumpkin seed oils and subtle nutty taste is due to the uniqueness of Styrian pumpkin seeds, the state of ripeness and the particular processing methods (Murkovic, Piironen, Lampi, Kraishofer, & Sontag, 2004; Siegmund & Murkovic, 2004) It is suspected that the region in which the plants are grown and climatic conditions also have an influence on the quality of this specialty oil Styrian pumpkin seed oil is one of the products protected by the EU as a regional specialty and is produced according to the specification as Protected Geographical Indication (PGI) In accordance with this protection, the use of the denotation ‘‘pure Styrian pumpkin seed oil’’ requires that this is 100% pure and results from a first pressing procedure in local mills The designation of origin must relate to a geographical area that must be either a protected name or geographical origin and the area specified must be where the pumpkins were grown and harvested Styrian pumpkin seed oil (PGI) traditionally produced from soft coated seeds of the Styrian oil pumpkin (Cucurbita pepo var styriaca, sometimes referred as var oleifera) This pumpkin variety is characterised by seeds which have lost their hard seed coats during ⇑ Corresponding author Tel.: +43 3842 402 1207; fax: +43 3842 402 1202 E-mail address: donata.bandoniene@unileoben.ac.at (D Bandoniene) 0308-8146/$ - see front matter Ó 2012 Elsevier Ltd All rights reserved http://dx.doi.org/10.1016/j.foodchem.2012.06.040 mutation in the 19th century Economic interests are the driving force for the development of new analytical tools to verify traceability of pumpkin seed and pumpkin seed oil, to improve quality control and the identification of falsifications in order to protect local production The rapidly increasing progress of multi-element and multiisotope techniques in elemental analysis has led to an increase of fingerprinting analysis of food samples which allows tracing back the origin of foodstuffs (Kelly, Heaton, Hoogewerff, 2005) As a method for determining the origin of food, e.g., fruit juices, wines, spirits, essential oils, milk and milk products, honey and olive oil, it is possible to analyse stable isotopic compositions determined by climatic and environmental conditions (Anklam, 1998; Kelly et al., 2005; Pillonel et al., 2003; Schmidt et al., 2005) This method involves the determination of the stable isotope amount ratios of elements like hydrogen, carbon, nitrogen, oxygen or sulphur Measurements of radioactive or radiogenic constituents, for example strontium 90Sr and 87Sr respectively may also give important information on the geographic origin of food products The analysis of isotopes of the main elements makes the method very robust and forgery-proof, since an artificial modification is very difficult The isotopic signature of a product may be the fingerprint of environmental and production-related conditions Since each region is unique in a specific manner, the isotopic patterns of products of different origin are different A determination of the geographic origin is therefore possible due to the different environmental parameters, like the composition of the regional rainfall, soil composition, etc But analysis of the stable and radiogenic isotope ratios as well as radioactive isotope amount contents only allow 1534 D Bandoniene et al / Food Chemistry 136 (2013) 1533–1542 separating geographically distant regions In addition the analysis of stable isotope ratios is expensive and time consuming, but the combination of two complementary methods such as stable isotope ratios with major and trace elemental data, is very suitable (Kelly et al., 2005; Pillonel et al., 2003) The geographically/geologically sensitive parameters like element traces composition, in particular the row of concentrations of all rare earth elements (REE or lanthanoids), are of significant relevance in order to allow for a spatially resolved distribution Several major and trace elements, especially (REE), have also been used successfully for the identification of the authenticity of wine, cheese, olive oils, honey, vegetables like onion, tomatoes, and others (Anklam, 1998; Ariyama, Horita, Yasui, 2003; Augagneur, Medina, Szpunar, Lobinski, 1996; Benincasa, Lewis, Perri, Sindona, Tagarelli, 2007; Bettinelli et al., 2005; Jakubowski, Brandt, Stuewer, Eschnauer, Görtges, 1999; Pillonel et al., 2003; Sun, Danzer, Thiel, 1997; Zeiner, Steffan, Juranovic Cindric, 2005) A great number of different edible oils, for example in olive oil, have been investigated for their trace element content and distribution, however the knowledge about the trace and ultra-trace element content in pumpkin seed and pumpkin seed oil is very sparse (Joebstl, Bandoniene, Meisel, Chatzistathis, 2010) Currently neither data published by other researches of concentrations of REE or of stable isotope amount ratios in pumpkin seed and pumpkin seed oil have been published The non-essential trace element distribution is, in contrast to many organic components, strongly dependent on the composition of the soil, so that such an analysis may allow distinguishing even between spatially closer related regions It is known through geochemical studies that the distribution pattern of the REE can be used for the identification of the petrologic origin of rocks and minerals (Henderson, 1984) The composition of most inorganic components in soil is directly related to the underlying rock which in turn is related to the local and regional geology The correlation between concentrations or distribution of REE in soil and for example plant oil of the same geographical origin is unknown, but in preliminary studies it was found, that the REE in plants also have characteristic patterns geologically related to the composition of most soils (Markert, 1993; Semhi, Chaudhuri, & Clauer, 2006) Therefore, it can be assumed that the REE distribution in pumpkin seed oils varies according to their origin and as such it can be supposed that a suitable statistical treatment on REE data allows a geographical characterisation of different pumpkin seed oils The presented work is part of a larger project (2006–2011) that was aiming to identify the geographic origin of pumpkin seed oil (Joebstl et al., 2010) The preliminary results of the project was published by Joebstl et al (2010) and demonstrated the possibility to use the REE as fingerprint for determination the geographical origin of pumpkin seed oil from even smaller regions within Austria (Lower Austria and Styria) The previous study for classification of oil samples in relations to their geographical origin based only on REE content data was extended by integrating other element traces and by taking samples from other non-Austrian (China and Russia) pumpkin seed oils during several years This work concentrated on the discrimination of Austrian samples as a whole without separation between PGI and non PGI, as the latter distinction is of minor relevance for customers and producers As China and Russia are the worldwide largest producers of pumpkin seeds we concentrated on these two countries only A robust discrimination model was developed to allow the verification of the geographic origin of unknown pumpkin seed (extracted oil) samples In addition to the regional differences, the content of the trace elements in pumpkin seed oils depends on many different factors, hence a systematic study of which, is one of the main focus of our study Systematic homogeneity and repeatability studies, REE distribution in different parts of pumpkins, climate and seasonal influences, influence of oil processing, degree of ripeness and other factors, had to be investigated to understand REE transport from the soil to plant and REE behaviour in the plant as well as to proof the stability of the method The stability of the method is essential for a correct classification of pumpkin seed oil origin with a statistical model To achieve this goal, influences on the stability of the classification method were quantified by several specific experiments and ultimately integrated in a robust statistical tool to identify the geographical origin which can prevent the possibility of fraud Experimental 2.1 Sampling Based on the preliminary study (Joebstl et al., 2010) a more systematic sampling strategy was planned to answer the following questions: the homogeneity of the REE distributions of soil within a field and REE distribution of soil amongst fields of different geographic origin and the influence of annual weather variations, homogeneity of the pumpkin seed and as a consequence the extracted oil composition For the homogeneity of soil samples collected in five agricultural farms in Austria namely Gleisdorf (Styria, Field 1), Wies (Styria, Field 2), St Bartholomä (Styria, Field 8), Jennersdorf (Burgenland, Field 4), Dobersberg (Lower Austria, Field 5) and in an agricultural farm in Hungary (Öczed, Field 3) The area of each field is approximately ha, only the field in Wies is smaller (approximately of 200 m2) For this purpose the total area of each field was parted into 25 units (20 Â 20 m), and Wies (Field 2) area into 18 raster each of 3.3 Â 3.3 m respectively From each raster 10 laboratory sampleswere taken (evenly distributed) and also from two depths (0–5 cm and 5–10 cm from the soil surface) All together 50 samples (36 samples for Wies) of soil per sampling target were collected The soil samples were collected in spring, prior to the application of fertilizers to the soil and cultivation of the pumpkins In order to prove the influence of the year to year weather changes on REE distribution of soil, REE contents of the soils in all the fields during years were investigated For this study only composite samples (a combination of 10 increments randomly distributed over the sampling target) were collected To test the homogeneity of the REE content distribution of pumpkin seeds within a field, pumpkins from each of the 18 subfields (raster) from Wies (Field 2) were collected and investigated individually The seeds of the individual pumpkins were air dried, and 18 composite samples consisting of the seeds within each raster analysed For testing the variation of REE concentrations during the ripeness period of two months (end of August until end of October) every week four pumpkins from the same field in Wies (Field 2) were sampled The subsamples of pumpkin flesh and pumpkin seed from the four pumpkins were homogenized and analyzed separately The variation of the trace elements distribution and homogeneity in different parts of pumpkin in relation to soil of the assured provenance was tested on pumpkin flesh, pumpkin seeds, the oil extracted from the seeds (Soxhlet) and oil-extraction cake In addition the related topsoil from the two selected locations Wies and St Bartholomä, both in Styria, were collected From each raster of the same field one pumpkin was taken and the different parts of these were analysed One pumpkin leave sample from each field (Wies and St Bartholomä) was also collected The influence of the oil processing in the mill on the REE distribution in pumpkin seed oil was tested by preparing oil samples from the seeds from the individual study fields and comparing the results with the data obtained from the oil obtained from the same subsample via Soxhlet extraction in our laboratory For this task all oils were produced under controlled conditions in one mill only (Grabersdorf, Styria) D Bandoniene et al / Food Chemistry 136 (2013) 1533–1542 Climate and annual weather influences on the REE and other trace element distribution were examined using the pumpkin seed oil samples extracted from the seeds of Austrian origin sampled over years 2006–2009 (from the same farmers and locations) Approximately 660 pumpkin seed samples from different regions in Austria, China and Russia were collected over years (2006–2009) for a systematic investigation of the geographic origin using multivariate data analysis Austrian and Russian seeds were sampled from seeds from one breed only The most common breed ‘Gleisdorfer Ölkürbis’ was selected for this study to avoid additional influence from the type of seed used by the farmers The Chinese seeds were of different kind but all were similar in having no hard shell and with a soft skin only 2.2 Sample preparation All soil samples collected were dried at ambient air temperature and then sieved to obtain the