Sandra Ned2eral NakicDesanka RadeDubravka SkevinDubravka StruceljZeljko MokrovcakMartina Bartolic

Faculty of Food Technologyand Biotechnology,University of Zagreb,Zagreb, Croatia

Chemical characteristics of oils from naked andhusk seeds of Cucurbita pepo L.

Pumpkin seed oils from naked and husk pumpkin seeds, produced by an industrialprocess and by laboratory extraction, were evaluated for fatty acid composition,tocopherol, sterol and squalene content. The major fatty acids in the oils from bothvarieties were oleic, linoleic and palmitic acid, followed by stearic acid. The ratios ofmonounsaturated to polyunsaturated fatty acids for husk and naked seed oils wereabout 0.60 and 0.75, respectively. Analysis of tocopherols in industrially pressed andlaboratory-extracted oils showed that husk seed oils had higher amounts of totaltocopherols than naked seed oils. Oils extracted in the laboratory had higher amountsof tocopherols than industrial oils. Pumpkin seed oil, in general, had a high level ofsqualene, which was higher in husk seed oils than in naked seed oils and in extractedthan in pressed oils. The total amount of sterols was higher in husk than in naked seedoils and in extracted oil samples. The main sterols were D7-sterols and their contentwas similar in all samples, but the content of D5-sterols was higher in oil samples ofhusk pumpkin seed and in extracted than in pressed oils.

Keywords: Pumpkin seed oil, fatty acids, tocopherols, squalene, sterols.

1 Introduction

Pumpkin seed oil is obtained from the seeds of the plantCucurbita pepo L. It is mainly produced in the southernparts of Austria, in Slovenia, Hungary, Germany and in thenorth of Croatia. The seeds can also be eaten as them-selves and show good results in the therapy of small dis-orders of the prostate gland and the urinary bladder [1].

The oil is dark greenish in color and has a typical nutty androasty flavor. It is produced from husk and naked varietiesof pumpkin seeds by mechanical methods. After crush-ing, (husk seed must be previously dehulled) the seedsare roasted at about 100–120 7C and then pressed atelevated temperatures. The oil is consumed without fur-ther treatments as salad oil and it consists mainly of tri-acylglycerols (about 98%) which coexist with non-tri-acylglycerols or minor components [2].

The composition of fatty acids in pumpkin seed oildepends on many factors (variety, climatic conditions),but in general, the dominant fatty acids are palmitic,stearic, oleic and linoleic acid [2–4].

Minor components include numerous chemical com-pounds, e.g. tocopherols, hydrocarbons, sterols, alco-hols, phospholipids and others. These minor lipid com-

pounds have proven of interest to food analysts becausetheir composition and ratios can provide a “fingerprint”for edible oils. Several classes of these compounds canbe present in oil and act as anti- or pro-oxidants, or theycan be helpful in preventing diseases and promotinghealth [5].

Tocopherols have many applications in foods and phar-maceuticals as natural antioxidants [6]. In oils, they arepresent in different isomeric forms: a-, b-, g-, d-tocopher-ols, and four closely related tocotrienols. The content oftocotrienols in oils is generally much less than that of theirtocopherols, with the exception of palm and wheat germoils [5].

Squalene, an aliphatic triterpenoid hydrocarbon with sixisoprene units is an intermediate compound in the bio-synthesis of sterols. It is generally present in variablequantities in the lipid fraction of all animals and plantsand is mainly found in non-edible shark liver oil. Virginolive oil is a major source of phytosqualene [7, 8], whichis also regarded as partially responsible for the beneficialeffects of olive oil against certain cancers. Epidemio-logical studies have demonstrated that increased dietaryintake of olive oil is associated with a small decrease orno increase in the risk of breast cancer. It is proposedthat the high squalene content of olive oil is a majorfactor in the cancer risk-reducing effect [9]. Psomiadouand Tsimidou [8] found that squalene also plays a con-fined role in virgin olive oil stability even at low tempera-tures.

Correspondence: Sandra Ned2eral Nakic, Faculty of Food Tech-nology and Biotechnology, University of Zagreb, Pierottijeva 6,10000 Zagreb, Croatia. Phone: 1385 1 4605279, Fax: 1385 14605072, e-mail: snedjer@pbf.hr

936 DOI 10.1002/ejlt.200600161 Eur. J. Lipid Sci. Technol. 108 (2006) 936–943

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Eur. J. Lipid Sci. Technol. 108 (2006) 936–943 Chemical characteristics of pumpkin seed oil 937

However, very little is known about squalene in other plantoils, particularly in pumpkin seed oil.

Sterols are used in order to determine the identity of an oil,and to detect the addition of cheap oils to more expensiveones [10–12]. Most plant oils contain predominantly D5-sterols, while D7-sterols are specific for pumpkin seed oil.These D7-sterols are supposed to give pumpkin seed oil abeneficial effect in the treatment and prophylaxis of dis-orders of the prostate gland and the urinary bladder [13].

Since nowadays much more naked pumpkin seed isprocessed, there is less data in the literature aboutpumpkin seed oil obtained from husk seed. However,due to the fact that factories in Slovenia and NorthernCroatia still use significant amounts of husk pumpkinseed for oil production, the aim of this study was tocompare the chemical characteristics of pumpkin seedoils obtained from husk and naked seed. It was impor-tant to determine the differences in their fatty acid com-position as well as the content and composition of themain minor compounds, namely tocopherols, sterols,and especially squalene, the content of which in pump-kin seed oil has so far not been investigated. Pumpkinseed oils obtained by an industrial process were com-pared with oils extracted in the laboratory, to assess thecomposition of the investigated compounds in thepumpkin seed and the effect of the actual productionprocess on changes in their content. In addition, labora-tory extraction of pumpkin seeds enabled better com-parison of the oils because they were obtained under thesame experimental conditions.

2 Materials and methods

2.1 Samples

Six different pumpkin seed samples with husk and sixwithout husk (naked) together with twelve industrialpumpkin seed oils produced from each of these seedswere obtained from factories in West Slovenia and NorthCroatia. All seed samples were of domestic origin andharvested in 2004 to exclude the influence of climatic andgeographical conditions on the results.

Each pumpkin seed sample was also extracted by hex-ane in the laboratory, in several batches, to obtain anamount of oil sufficient for the analyses. In one batch, 10 gpumpkin seeds was ground (the husk from husk seedswas removed manually prior to rinding) and extracted inthe laboratory for 4 h with hexane in a Soxhlet apparatus.The solvent was removed by rotary evaporation at 40 7C,and the oil was immediately analyzed or stored in sealedbottles at 220 7C until analysis. Samples for the determi-

nation of tocopherols were prepared by cold hexaneextraction. About 10 g of ground pumpkin seeds wasextracted with 30 mL n-hexane and filtered throughunhydrous Na2SO4. The solvent was then evaporated at40 7C and the obtained oil was immediately analyzed byHPLC.

Analyses of each oil sample were carried out in duplicateand all results were expressed as mean values of six oilsamples.

The mean oil contents of the seed samples used in theexperiments were 44.74 6 1.69% for naked and36.89 6 1.34% for husk seeds, and the mean moistureswere 6.24 6 0.84% and 7.15 6 0.79%, respectively.

2.2 Chemicals

Standards [fatty acid methyl esters (FAME), squalene, 5a-cholestanol, cholesterol, uvaol, b-sitosterol, campesterol,stigmasterol, a-, g- and d-tocopherol] and specific chem-ical reagents for sterol determination were supplied bySigma Chemical Co. (St. Louis, MO, USA). All otherchemicals were of analytical grade, obtained from MerckKGaA (Darmstadt, Germany), and used without furtherpurification.

2.3 Apparatus

All gas chromatography (GC) analyses were carried outon an ATI Unicam 610 instrument (Cambridge, UK)equipped with a split-injector and flame ionization detec-tor (FID).

For HPLC analysis of tocopherols, a Varian ProStar HPLCequipped with a Varian ProStar 363 fluorescence detectorwas used.

2.4 Fatty acid composition

FAME were prepared according to the standard method[14]. The fatty acid profile was determined by gas chro-matographic separation of their methyl esters [15] on acapillary column (J&W Scientific DB-23, 30 m 6 0.25 mm6 0.25 mm). The temperatures of the injector and detec-tor were set at 250 7C. The initial oven temperature was170 7C. This temperature was maintained for 8 min andthen increased at a rate of 2 7C/min to 190 7C, which washeld for 7 min. Helium was used as the carrier gas at aflow rate of 0.87 mL/min and the injection volume was0.3 mL. The FAME peaks were identified using FAMEstandards. The fatty acid composition is expressed asweight percentage of total (internal normalization meth-

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938 S. Nederal Nakic et al. Eur. J. Lipid Sci. Technol. 108 (2006) 936–943

od). Chromatography software (Unicam 4880 chroma-tography data system) was employed for data collectionand processing.

2.5 Tocopherol analysis

Tocopherols were analyzed by HPLC according to thestandard method [16]. Of oil samples, 0.1 g was weighedinto a 10-mL volumetric flask and diluted to the mark withn-hexane. The individual tocopherols were separated ona Restek Pinnacle II silica column, 15 cm 6 4.6 mm i.d.(5 mm) which was held at 30 7C. Detection was performedat an excitation wavelength of 290 nm and an emissionwavelength of 330 nm. A solution of 0.7% propan-2-ol inn-hexane was used as eluent at a rate of 0.60 mL/min.Tocopherol standards (a-, g- and d-tocopherol) were usedfor the setup of calibration curves that covered con-centrations from 5 to 750 mg/kg of tocopherols in oil.

2.6 Unsaponifiable fraction and squaleneanalysis

Squalene was determined by GC of the complete unsapo-nifiable fraction according to a modification of the methodthat Giacometti developed for virgin olive oil [17]. Instead ofeicosanol as proposed by the method, 5a-cholestanol wasused as an internal standard, because eicosanol co-elutedwith an unknown peak in pumpkin seed oil. The unsaponifi-able fraction was prepared according to the method forsterol determination [18] and finally made up in a 5% tri-chlormethane solution. Of this solution, 100 mL was sily-lated with 300 mL pyridine/hexamethyldisilazan/trimethyl-chlorsilan (10 : 2 : 1) and the volume of 0.2 mL was injectedinto a gas chromatograph equipped with a DB-17 capillarycolumn (30 m 6 0.32 mm 6 0.25 mm) containing (50%phenyl)-methylpolysiloxane stationary phase. Helium wasused as carrier gas at a flow rate of 0.39 mL/min. The tem-perature of the injector was set to 290 7C and that of thedetector to 300 7C. The temperature of the column ovenwas increased from initially 180 7C at a rate of 6 7C/min to270 7C, which was kept for 30 min. The total run time was45 min. Identification of the squalene peak was made by theuse of pure squalene standard.

2.7 Sterol analysis

The sterol fraction was separated from the unsaponifiablematter by thin-layer chromatography and analyzed by GC[18]. For the analysis of the sterol fraction, the gas chro-matograph was equipped with a DB-17 capillary column(30 m 6 0.32 mm 6 0.25 mm) and used under the sameconditions as in the analysis of squalene. The injection

volume was 0.5 mL. Quantification of all sterols was basedon an internal standard method using 5a-cholestanol thatwas added to the analyzed oil prior to saponification. In-dividual D5-sterol peaks were identified and calibrated byavailable sterol standards. However, since D7-sterols arenot commercially available, they were identified by com-parison with relative retention time data from the literature[11, 18, 19] and their contents were calculated using thecalibration curve of b-sitosterol as the main sterol com-pound in other vegetable oils.

2.8 Statistical analysis

Statistical analysis was performed using the STATISTICA7.1. software [20]. Two-way factorial ANOVA was used todetermine the effect of seed variety, the production pro-cess and their interaction on the chemical characteristicsof the analyzed oils.

3 Results and discussion

Tab. 1 shows the fatty acid compositions of the analyzedpumpkin seed oil samples. In all samples, the dominantfatty acids were palmitic, stearic, oleic and linoleic acid.The values were in line with those reported by otherauthors [2–4, 21].

The fatty acid content differed depending on the pumpkinseed variety. Oleic acid was significantly higher (p �0.05)in the oils of naked seed, compared to linoleic acid. Theratio of monounsaturated to polyunsaturated fatty acidswas also higher in naked than in husk seed oils (about0.75 and 0.60, respectively). Two-way factorial ANOVAalso showed a statistically significant effect (p �0.05) ofthe seed variety on the content of myristic (14:0) andheptadecanoic (17:0) fatty acid. The fatty acid composi-tion of the oils obtained by pressing and extraction did notdiffer much, and statistical analysis showed a significantinfluence (p �0.05) of the process only on the content ofheptadecanoic (17:0) fatty acid.

The fatty acid composition of an oil can be an indicator ofits oxidative stability and nutritional quality. Generally, it isaccepted that the higher the degree of unsaturation of anoil, the more susceptible it is to oxidative deterioration. Onthe other hand, there are consistent data to recommend areduction in saturated and a moderate increase in mono-unsaturated and n-3 and n-6 polyunsaturated fatty acidsin human nutrition in order to prevent coronary heart dis-ease and other diseases [22, 23].

However, the oxidative stability of oils depends not onlyon the fatty acid composition, but also on the presence ofminor components that can have antioxidative effects.

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Eur. J. Lipid Sci. Technol. 108 (2006) 936–943 Chemical characteristics of pumpkin seed oil 939

Tab. 1. Fatty acid composition (wt-% of total FA, mean 6 SD, n = 6){ in pumpkin seed oils fromnaked and husk pumpkin seeds obtained by industrial process and laboratory extraction.

Fatty acids Naked seed oil Husk seed oil

Industrial Laboratory Industrial Laboratory

14:0{ 0.10 6 0.01 0.10 6 0.01 0.08 6 0.02 0.09 6 0.0116:0 12.01 6 0.48 11.97 6 0.48 12.00 6 0.83 11.91 6 0.8716:1 0.13 6 0.06 0.15 6 0.06 0.17 6 0.07 0.18 6 0.1017:0{,§ 0.07 6 0.01 0.06 6 0.01 0.10 6 0.02 0.08 6 0.0118:0 5.25 6 0.62 5.24 6 0.61 4.97 6 0.61 4.87 6 0.6418:1{ 35.12 6 4.31 34.75 6 4.04 30.46 6 2.08 30.27 6 2.0118:2{ 46.58 6 4.41 47.01 6 3.73 51.51 6 2.19 51.88 6 1.9418:3 0.25 6 0.10 0.24 6 0.09 0.25 6 0.05 0.23 6 0.0320:0 0.32 6 0.04 0.32 6 0.10 0.30 6 0.08 0.32 6 0.0720:1 0.09 6 0.01 0.08 6 0.02 0.08 6 0.02 0.08 6 0.0122:0 0.08 6 0.02 0.08 6 0.04 0.08 6 0.02 0.08 6 0.05

{ Values are expressed as average of six oil samples analyzed individually in duplicate.{ Results are significantly influenced by seed variety (p �0.05).§ Results are significantly influenced by production process (p �0.05).

The effect of an antioxidant activity is based on thequenching of free radicals. Thereby, antioxidants can stopthe chain reaction and the accumulation of free radicalsand prevent damages caused by the oxidation of lipids[24].

Tocopherols are widespread natural antioxidants, andtheir amount in oils depends on the kind of oil and isprobably governed by the content of unsaturated fattyacids. The content of tocopherols in oils is also affectedby the processing conditions [5, 25]. According to Mur-kovic [26], g-tocopherol in pumpkin seeds was in therange of 41–620 mg/kg.

The total amount of tocopherols (Fig. 1, Tab. 2) in the an-alyzed samples was significantly higher in the oils of huskthan of naked seed. The mean values of total tocopherolsin industrial oils of husk and naked seeds were 651 and454 mg/kg, respectively. Solvent extracted oils of huskand naked seed contained significantly higher amounts oftocopherols (p �0.05) than industrially pressed oils. In allanalyzed samples, the content of a-tocopherol was about50 times lower than that of g-tocopherol. These results arenot in accordance with those already published [26, 27]describing contents of a-tocopherol being only 5–10 times lower than the contents of g-tocopherol. How-ever, many authors [26–29] show that total and individualtocopherol contents in vegetable oils depend on severaldifferent factors (e.g. cultivar, climate, extraction condi-tions, method of determination). In addition, Murkovic etal. [26] state that the biosynthesis of a- and g-tocopherolis not strictly coupled and that the degradation of different

Fig. 1. HPLC chromatogram of tocopherols in industriallypressed husk pumpkin seed oil. For conditions, seeMaterials and methods.

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940 S. Nederal Nakic et al. Eur. J. Lipid Sci. Technol. 108 (2006) 936–943

Tab. 2. Total tocopherol content (mean 6 SD, n = 6){ and composition (wt-% of total tocopherols,mean 6 SD){ in pumpkin seed oils from naked and husk pumpkin seeds obtained by industrialprocess and laboratory extraction.

Tocopherols Naked seed oil Husk seed oil

Industrial Laboratory Industrial Laboratory

a-tocopherol 1.65 6 0.59 2.04 6 1.20 1.52 6 0.78 1.67 6 0.98g-tocopherol§ 97.15 6 0.78 96.08 6 1.40 97.31 6 0.75 96.02 6 1.41d-tocopherol§ 0.86 6 0.45 1.88 6 0.86 1.17 6 0.75 2.32 6 1.54Total [mg/kg]{,§ 454 6 48 520 6 57 652 6 80 709 6 83

{ Values are expressed as average of six oil samples analyzed individually in duplicate.{ Results are significantly influenced by seed variety (p �0.05).§ Results are significantly influenced by production process (p �0.05).

tocopherols occurs at different rates. The individualtocopherols from two seed varieties showed no differ-ences in composition, while the content of g-tocopheroland d-tocopherol was significantly influenced (p �0.05)by the production process. g-Tocopherol was higher,while d-tocopherol was lower in pressed than in extractedoils.

The antioxidant activity of tocopherol has been studiedextensively. It was found that the g- and d-forms possessa much higher antioxidant activity than the a- and b-forms; however, a-tocopherol is considered to have ahigher vitamin potency than any other tocopherol isomer[30].

Murkovic and Pfannhauser [31] reported that vitamin Ehas no influence on the oxidative stability of pumpkinseed oil, and that the stability of this oil is influenced pri-marily by the ratio of linoleic to oleic acid.

The data for the unsaponifiable fraction content deter-mined in the industrial and the laboratory-extracted oils ofhusk and naked pumpkin seeds are shown in Tab. 3.These data showed a significant effect (p �0.05) of theproduction process on the unsaponifiable fraction con-tent, which was higher in the extracted than in theindustrially pressed oils. Fig. 2 shows the gas chromato-gram of the unsaponifiable fraction in industrially pressedhusk pumpkin seed oil.

Besides the peak of squalene, it also contains manypeaks eluting before and after the peak of squalene. Thepeaks at the beginning of the chromatogram are sup-posed to belong to aliphatic alcohols [17]. They are leftunidentified at this point because we were unable to findthe right standards for their identification. The peaks atthe end of the chromatogram belong to sterols, but theywere not quantified in this analysis, because some of the

Fig. 2. Gas chromatogram of the unsaponifiable fractionof industrially pressed husk pumpkin seed oil (n.d., notdetermined). For conditions, see Materials and methods.

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Eur. J. Lipid Sci. Technol. 108 (2006) 936–943 Chemical characteristics of pumpkin seed oil 941

Tab. 3. Content of unsaponifiable fraction and squalene (mean 6 SD, n = 6){ in pumpkin seed oilsfrom naked and husk pumpkin seeds obtained by industrial process and laboratory extraction.

Naked seed oil Husk seed oil

Industrial Laboratory Industrial Laboratory

Unsaponifiable [% of oil]§ 1.75 6 0.35 2.40 6 0.38 1.83 6 0.41 2.53 6 0.42Squalene [mg/kg]§ 2259 6 155 2962 6 774 2630 6 357 3513 6 1021

{ Values are expressed as average of six oil samples analyzed individually in duplicate.§ Results are significantly influenced by production process (p �0.05).

sterols that were present in lower contents could not bedetermined directly from the unsaponifiable fraction.Therefore, the sterol fraction was later isolated anddetermined on its own. The results presented in Tab. 3.show that pumpkin seed oil has, in general, a high level ofsqualene. Two-way factorial ANOVA did not show anysignificant influence of the pumpkin seed variety on thesqualene content, while its content was significantlyhigher (p �0.05) in extracted than in pressed oils. In huskseed oil its content was about 16%, and in naked seed oilabout 13% of the unsaponifiable matter, in both theindustrial and the extracted oil.

These data cannot be compared to the literature becausewe were unable to find any work done on squalene con-tent in pumpkin seed oil. Therefore, further research isneeded because the interest in the health benefits ofsqualene is steadily increasing and the potential effects of

its daily intake are being evaluated [32, 33]. Experimentalstudies have shown that squalene can effectively inhibitchemically induced colon, lung and skin tumor genesis inrodents. Findings of Chinethalapally et al. [34] strengthenthe hypothesis that squalene possesses chemo-pre-ventive activity against colon carcinogenesis.

Sterols can be present in oils as free compounds andesterified with fatty acids. According to the double bondin the ring, phytosterols are usually classified as D5- andas D7-sterols. Most plants contain predominantly D5-sterols, while D7-sterols are specific for only a few plantfamilies, e.g. Cucurbitaceae and Theaceae [35].

The composition of the sterol fraction of the investigatedpumpkin seed oils is presented in Fig. 3 and Tab. 4. Goodseparation of the sterol peaks was achieved by the use ofa capillary column of higher polarity, namely (50% phe-

Tab. 4. Total sterol content (mean 6 SD, n = 6){ and composition (wt-% of total sterols, mean 6 SD){

in pumpkin seed oils from naked and husk pumpkin seeds obtained by industrial process andlaboratory extraction.

Sterols Naked seed oil Husk seed oil

Industrial Laboratory Industrial Laboratory

Campesterol{,§ 0.74 6 0.15 1.15 6 0.24 1.81 6 0.67 2.56 6 0.33D5-Stigmasterol{ 0.82 6 0.15 0.85 6 0.11 1.04 6 0.34 1.31 6 0.1b-Sitosterol{,§,# 5.60 6 0.69 6.48 6 0.68 7.87 6 0.82 12.08 6 0.65Spinasterol{,§ 26.81 6 0.97 23.90 6 1.87 24.44 6 0.34 19.88 6 0.73D7,22,25-Stigmastatrienol{,# 25.71 6 1.04 26.24 6 0.29 25.27 6 1.00 24.03 6 0.78D7,25-Stigmastadienol 21.92 6 0.71 22.28 6 1.56 21.36 6 1.26 22.68 6 1.17D7-Stigmasterol{,§ 1.99 6 0.35 1.73 6 0.18 1.75 6 0.13 1.46 6 0.14D7-Avenasterol 16.41 6 0.83 17.38 6 1.34 16.47 6 1.29 16.00 6 1.3Total [mg/kg]{,§ 2931 6 210 3172 6 147 3452 6 267 3852 6 157

{ Values are expressed as average of six oil samples analyzed individually in duplicate.{ Results are significantly influenced by seed variety (p �0.05).§ Results are significantly influenced by production process (p �0.05).# Results are significantly influenced by interaction of seed variety and production process

(p �0.05).

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942 S. Nederal Nakic et al. Eur. J. Lipid Sci. Technol. 108 (2006) 936–943

Fig. 3. Gas chromatogram of the sterol fraction ofindustrially pressed husk pumpkin seed oil. For condi-tions, see Materials and methods.

nyl)-methylpolysiloxane instead of (5% phenyl)-methyl-polysiloxane that is proposed by the method. In somepreliminary investigations, when a less polar column wasused, peaks of b-sitosterol, stigmastatrienol and stig-mastadienol co-eluted and it was impossible to separatethem by changing the temperature program or the flowrate of the carrier gas.

The data showed that the total amount of sterols inpumpkin seed oils was significantly higher (p �0.05) in thehusk seed oils and in the laboratory-extracted oils com-pared to the naked seed and the industrial oils, respec-tively.

The main sterols of these oils were, as expected, specificD7-sterols (D7,22,25-stigmastatrienol, spinasterol,D7,25-stigmastadienol and D7-avenasterol). However, theamounts of D5-sterols for naked and husk pumpkin seedoils were clearly different. The values for industrial naked

seed oils were 7.16% ofD5-sterols, which is in accordancewith the data indicated by other authors and with Croatianlegislation [35, 36], while the values for the industrial huskseed oils were much higher (10.72%). Extracted husk seedoils had even a higher content of D5-sterols (15.95%).Results of two-way factorial ANOVA showed that differentpumpkin seed varieties (husk and naked) affected thecontent of campesterol, stigmasterol, b-sitosterol, spi-nasterol, stigmastatrienol and D7-stigmastenol with sta-tistical significance (p �0.05). b-Sitosterol, campesterol,spinasterol and D7-stigmastenol were significantly influ-enced (p �0.05) by the production process (industrialprocess or laboratory extraction), while b-sitosterol andstigmastatrienol (p �0.05) were significantly influenced bythe interaction between variety and process. Murkovic etal. [37] state that no clear destruction of sterols or changein sterol profile was found during the production process ofpumpkin seed oil, i.e. roasting. However, the influence ofroasting on the content of individual D5- and D7-sterolscould not be determined because some of them co-eluted;so it is difficult to comment our results in light of thosefindings. Differences between the contents of D5- and D7-sterols in pressed and extracted oils in our work could haveoccurred due to the greater degradation ofD5-sterols thanD7-sterols at elevated temperature during the roasting ofpumpkin seed in the industrial production process, or thelower conversion of D5-sterols to oil in the industrialpressing. Anyhow, this observations need to be illumi-nated in future investigations because of the fact thatpumpkin seed oil is often adulterated by the addition ofcheaper vegetable oils and that admixture of these oils ismainly detected by elevated concentrations of D5-sterols(especially b-sitosterol).

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[Received: July 17, 2006; accepted: August 30, 2006]

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