J Am Oil Chem Soc (2013) 90:641–646 DOI 10.1007/s11746-013-2209-0
ORIGINAL PAPER
Rapid Detection and Quantification by GC–MS of Camellia Seed Oil Adulterated with Soybean Oil Jia Xie • Tianshun Liu • Yingxin Yu Guoxin Song • Yaoming Hu
•
Received: 10 October 2012 / Revised: 16 December 2012 / Accepted: 17 January 2013 / Published online: 6 February 2013 Ó AOCS 2013
Abstract Camellia seed oil with high nutritional value is widely used in southern China and southeastern Asia for cooking. Due to the high price of camellia seed oil, fraudulent traders blended the oil with inexpensive oils to increase profits. In this paper, a new method was introduced to detect the adulteration of camellia seed oil with soybean oil by GC–MS with consideration of a parameter which was defined by the total content of oleic and linoleic acid, the oleic to linoleic acid ratio and the content of linolenic acid. Oils samples were prepared by blending pure camellia seed oil with pure soybean oil at levels from 1 to 50 %. Fatty acids esterified by TMSH and TBME in seconds were separated and identified by GC–MS. The detection limit of adulteration was as low as 5 %, and even much lower than 5 % for most kinds of camellia seed oil, which was lower than those measured by other methods. All the results indicated that this simple, accurate and rapid method can also be recommended for the authentication of olive oil with some modification. Keywords Adulteration Camellia seed oil Linoleic acid Oleic acid Linolenic acid Soybean oil
J. Xie T. Liu G. Song (&) Y. Hu (&) Research Center of Analysis and Measurement, Fudan University, Shanghai 200433, People’s Republic of China e-mail:
[email protected] Y. Hu e-mail:
[email protected] Y. Yu Institute of Environmental Pollution and Health, School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, People’s Republic of China
Introduction Titled as ‘‘eastern olive oil’’, camellia seed oil is widely used in China and some other Asian countries. It is extracted from the seed of camellia which is mainly grown in Zhejiang, Hunan, Guangxi and Jiangxi provinces of China [1]. Characterized by high contents of oleic and linoleic acids, camellia seed oil has a chemical composition similar to olive oil. According to some reports, camellia seed oil has lots of health benefits, such as antitumor and antioxidant properties. It has also been shown to prevent coronary heart disease, inhibit atherosclerosis, and regulate the immune system [2]. Camellia seed oil has become one of the most frequent targets for adulteration by cheap oils, especially soybean oil, to gain economic profits because of its high price and huge potential market. Adulteration of commercial edible oils not only damages the interests of consumers and related industries, but also poses a threat to human health. It is therefore necessary to establish a simple and rapid method to detect the adulteration of camellia seed oil with soybean oil. Based on the physical properties or chemical components of edible oils, many methods have been developed in the past to assess the adulteration of high price oils. Because of its advantages of relatively fast, non-destructive and cost effective, Fourier transform infrared spectroscopy (FTIR) has been widely used for authentication of cod-liver oil [3, 4], olive oil [5] and palm oil [6]. Stable carbon isotope technology [7, 8], near infrared spectroscopy (NIR) [9, 10], headspace-mass spectrometry [11] and polymerase chain reaction-capillary electrophoresis-single strand conformation polymorphism (PCR-CE-SSCP) [12, 13] were used to detect olive oil adulteration. Mid-infrared spectra [14], low field nuclear magnetic resonance (LF-NMR) [15]
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Materials and Methods Samples and Reagents Ten brands of pure camellia seed oils and eight brands of pure soybean oils were purchased from local markets in Shanghai, China. The pure camellia seed oils were obtained from the seeds of Camellia oleifera grown in Zhejiang, Hunan, Guangdong, Guangxi and Jiangxi provinces of China. The soybean oil samples were derived from the milling of soybeans which planted in different regions of China. We studied and chose a representative camellia seed oil (Scented Fuzhou Cereals, Oils & Foodstuffs Co., Ltd, China). In our study we also found that there were small differences in the compositions of the eight soybean oils, particularly the oleic acid content. Therefore, the
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Relative Abundance
and Raman spectroscopy [16] are other popular analytical methods in routine measurements in monitoring the adulteration of edible oil. But now, chromatographic techniques, including highperformance liquid chromatography (HPLC) [17, 18] and gas chromatography-mass spectrometry (GC–MS) [19, 20], gradually become the most important and common technologies to detect the adulteration. HPLC is usually applied to the quantification of triacylglycerides and tocopherols while GC–MS is a common separation tool for the analysis of fatty acids and sterols. According to the summation of campesterol and stigmasterol percentages, it can determine the presence of corn, soybean, sunflower and cotton seed oils in olive oil [21]. Based on the contents of linolenic acid, sesame oil blended with soybean oil can be discriminated [19]. The ratio of fatty acid was also used to detect the contamination of olive oil by sunflower oil [22]. By the measurement of chemical compositions including fatty acids, triglycerides, sterols, tocopherols, and volatiles, Ramon and Ramon [20] reviewed the authentication of vegetable oils by chromatographic techniques. In recent years, more and more attention has been paid to the authentication of olive oils. But for camellia seed oil, little information about its authentication was available in the literatures. Detecting adulteration in camellia seed oil by electronic nose [23], attenuated total reflectance MIR, fiber optic diffuse reflectance NIR [24], and pattern recognition techniques [10] with a combination of chemometric tools have been presented. However, to our knowledge, there are no reports based on the contents of fatty acids (C18:1, C18:2 and C18:3) to detect blends of camellia seed oil and soybean oil by GC–MS so far. Therefore, the aim of the present study was to establish a simple, rapid and accurate method to detect the adulteration level of camellia seed oil with soybean oil by GC–MS.
J Am Oil Chem Soc (2013) 90:641–646
F A
B
C
H I G
J
L
D E
M
N
O R S P V
T
W(X)
U Q
Y
Z
Time(min)
Fig. 1 Standard mixtures of 26 fatty acid methyl esters (FAME). A-C14:0, B-C16:0, C-C16:1, D-C17:0, E-C18:0, F-C18:1n-11, G-C18:1n-9, H-C18:2n-6, I-C18:3n-6, J-C18:3n-3, K-C20:0, L-C20:1, M-C20:2n-6, N-C20:3n-6, O-C20:4n-6, P-C20:3n-3, Q-C20:5n-3, R-C22:0, S-C22:1, T-C22:2n-6, U-C22:4n-6, V-C22:3n-3, W(X)-C22:5n-3 or C24:0, Y-C24:1, Z-C22:6n-3
selected camellia seed oil was adulterated with soybean oil randomly to develop a method for detecting camellia seed oil adulteration. The levels of adulteration were as follows: 1, 2, 3, 4, 5, 10, 15, 20, 35, 45, and 50 % of the total weight. Thus, a total of 18 kinds of pure oils were collected and 11 kinds of blended oils samples were obtained. Standard mixtures of 26 fatty acid methyl esters (FAME) shown in Fig. 1, were purchased from Sigma-Aldrich (St. Louis, MO, USA). Trimethylsulfonium hydroxide (TMSH) and tert-butyl methyl ether (TBME) were obtained from Ai Keda Chemical Technology (Chengdu, China) and Acros organics (Belgium), respectively. Sample Treatment To analyze the fatty acid contents of the samples, fatty acids in oils were esterified by the method ISO 12966-3. And the corresponding FAME were extracted and analyzed using GC–MS. Briefly, 10 mg oil sample was weighed into a test tube, then 500 lL TBME was added into the test tube followed by 250 lL TMSH, and the mixture was shaken vigorously for about 30 s. The prepared samples were stored at 4 °C until analysis. GC–MS Analysis A Finnigan Voyager GC–MS instrument was used to quantify the concentrations of FAME. An AB-INNOWax highly polar capillary column (30 m 9 0.25 mm 9 0.25 lm, Abel, USA) coated with a 100 % polyethylene glycol stationary phase was used. The oven temperature was operated as follows: 120 °C (held for 1 min), raised from 120 to 170 °C at a rate of 20 °C/min, from 170 to 210 °C at a rate of 3 °C/min, from 210 to 250 °C at a rate of 20 °C/min, finally, held at 250 °C for 10 min. The
J Am Oil Chem Soc (2013) 90:641–646
injection temperature was set at 260 °C. Helium was used as the carrier gas with a flow rate of 1.0 mL/min. An injection volume of 1 lL was used with the split ratio of 100:1. The mass spectrometer was operated under a mode of electron impact (EI) at 70 eV with the scan ranges between 41 and 350 amu. The identification of FAME was done by comparing their retention time with those of standards. Statistical Analysis One-way analysis of variance, ANOVA (Tukey’s honest significant difference multiple comparison) was evaluated using SPSS statistics 12.0 (SPSS Inc., Chicago, USA). p values\0.05 were considered statistically significant. All adulteration level investigations were carried out in quintuplicate, and the analytical data were used for statistical comparison. The linear relationship between the linolenic acid contents and the adulteration levels was analyzed by Origin V8.0 (OriginLab, USA). It was also used to analyze the relationship between the defined adulteration parameter (AP) values and the adulteration levels.
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seed oils. In contrast, the contents of linoleic acid in the camellia seed oils ranged from 6.53 to 9.49 %, while linoleic acid in soybean oils were in the range of 50.6053.23 %. The other main unsaturated fatty acid (UFA) in the pure oil samples was linolenic acid (C18:3). The contents of linolenic acid in the pure camellia seed oils were in small amount accounted for only 0.05–0.27 % of the totals, however, much higher contents of linolenic acid with the range of 4.26–6.49 % were observed in the pure soybean oils. For the saturated fatty acids, their contents were much lower than those of unsaturated fatty acids which accounted for approximately 90 % in oil samples. The main saturated fatty acids in the camellia seed oils were palmitic acid (C16:0), stearic acid (C18:0), and arachidic acid (C20:0), which were comparable to those in soybean oils.
Results and Discussion Method Repeatability and Instrument Precision The method reproducibility was obtained by five independent prepared samples (soybean oil at a level of 20 %). The % relative standard deviation (RSD) was found to be 3.7 %. The instrument precision was assessed by five repetitive injections of the same sample solution, and the sample stability was investigated by analyzing the same sample solution at 0, 4, 8, 24, and 48 h (n = 5). The relative standard deviation of peak areas and retention time of five replicate runs of these components was B5 %. Profiles of Fatty Acids in Pure Camellia Seed and Soybean Oils The total ion chromatograms (TICs) of pure camellia seed oil and soybean oil are shown in Fig. 2a, b, respectively. The main compositions of fatty acids in the camellia seed oils and soybean oils were listed in Table 1. Oleic acid (C18:1) and linoleic acid (C18:2) were the predominant fatty acids in all of the oil samples. Oleic acid in the camellia seed oils accounted for 78.19–85.63 % of the total fatty acids, which was comparable with that in olive oils (77.64–81.60 %) [10, 25]. However, the oleic acid in soybean oils only accounted for 23.88–27.69 % of the total fatty acids, which was much lower than that of camellia
Fig. 2 The total ion chromatograms of pure camellia seed oil (a), and soybean oil (b)
Table 1 The contents of the main fatty acids (%) and the values of AP of pure camellia seed oils and soybean oils Camellia seed oil
Soybean oil
Palmitic acid (C16:0)
2.81–9.77
10.73–13.51
Stearic acid (C18:0) Oleic acid (C18:1)
1.29–3.21 78.19–85.63
3.70–4.67 23.88–27.69
Linoleic acid (C18:2)
6.53-9.49
50.60–53.23
Linolenic acid (C18:3)
0.05–0.27
4.26–6.49
Arachidic acid (C20:0)
0.02–0.38
0.20–0.43
176.39–210.85
18.06–41.18
AP
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As shown in Table 1, the contents of palmitic acid, stearic acid and arachidic acid in the camellia seed oils accounted for 2.81–9.77, 1.29–3.21, and 0.02–0.38 % respectively.
5
4
To detect soybean-oil adulterated camellia seed oil, pure camellia seed oil was blended with pure soybean oil at the levels from 1 to 50 %. The main fatty acids of the mixtures were listed in Table 2. As previously mentioned, the contents of oleic and linoleic acids were very different between camellia seed oil and soybean oil, which showed opposite trends in the mixtures. The percentage of linolenic acid in camellia seed oil was much lower than that in soybean oil. Thus, oleic acid, linoleic acid and linolenic acid might be used as discrimination parameters to detect camellia seed oil adulterated with soybean oil.
%Linolenic acid
Adulteration of Camellia Seed Oil with Soybean Oil 3
2
1
0 0
20
40
60
80
100
% soybean oil adulterated in camellia seed oil Fig. 3 The relationship between the linolenic acid contents and the adulteration levels
Linolenic Acid Used as an Adulteration Parameter The percentages of linolenic acid in pure and blended oil samples are listed in Tables 1 and 2. The results showed that the contents of linolenic acid in blended camellia seed oil samples were enhanced gradually with the increase in levels blended with soybean oil (Fig. 3). The relationship between linolenic acid and the adulteration level is expressed is the Eq. (1): X1 ¼ ðY 0:1105Þ=0:0452 R2 ¼ 0:982
ð1Þ
where Y % was the content of linolenic acid, X1 % was the adulteration level.
In our study, the contents of linolenic acid in pure camellia seed oils were in the range of 0.05–0.27 %. Considering the varieties of oil samples and data obtained from most reports, we set the value of linolenic acid at 0.4 % as a critical point, it indicated the existence of adulteration when the linolenic acid content accounted for more than 0.4 % in the camellia seed oil. Based on this criterion and Eq. (1), the adulteration of camellia seed oil could be detected at levels as low as approximately 6 % with soybean oil. Furthermore, this method can be applied to detect the adulteration of those oils which have a low
Table 2 The contents of the main fatty acids (%) and the values of AP of blended oils C16:0
C18:0
C18:1
C18:2
C18:3
C20:0
AP
CSO
3.34 ± 0.16a
3.21 ± 0.25
83.50 ± 2.55
7.66 ± 0.35
0.14 ± 0.01
0.36 ± 0.06
198.79
?1 %
4.20 ± 0.21*
3.33 ± 0.25
82.51 ± 1.58
7.99 ± 0.33
0.14 ± 0.02
0.32 ± 0.04
192.35
?2 %
3.71 ± 0.38
3.34 ± 0.16
82.21 ± 2.25
8.03 ± 0.18
0.16 ± 0.02
0.41 ± 0.08
191.06
?3 %
3.79 ± 0.55
3.32 ± 0.23
82.38 ± 1.95
8.61 ± 0.25
0.16 ± 0.01
0.35 ± 0.04
185.15
?4 %
4.15 ± 0.32*
3.22 ± 0.16
81.89 ± 1.70
8.72 ± 0.30
0.19 ± 0.04
0.44 ± 0.05*
182.63
?5 %
4.09 ± 0.79*
3.52 ± 0.16
81.19 ± 2.93
8.91 ± 0.65*
0.42 ± 0.08
0.39 ± 0.04
177.03 156.88
?10 %
4.46 ± 0.83*
3.34 ± 0.26
78.82 ± 2.24*
10.76 ± 0.89*
0.60 ± 0.07*
0.44 ± 0.03*
?15 %
4.87 ± 0.60*
3.43 ± 0.32
76.88 ± 2.12*
12.23 ± 0.33*
0.68 ± 0.03*
0.51 ± 0.05*
145.18
?20 %
5.37 ± 0.74*
3.76 ± 0.38*
73.65 ± 1.69*
14.40 ± 0.83*
0.78 ± 0.07*
0.60 ± 0.08*
131.40 106.63
?30 %
7.41 ± 0.50*
3.42 ± 0.51
67.12 ± 2.00*
19.02 ± 0.95*
1.48 ± 0.10*
0.57 ± 0.06*
?45 %
9.61 ± 0.35*
3.40 ± 0.70
58.01 ± 1.49*
24.10 ± 1.01*
2.78 ± 0.17*
0.67 ± 0.06*
78.38
?50 %
11.43 ± 0.51*
3.43 ± 0.47
52.76 ± 1.72*
27.58 ± 1.97*
3.06 ± 0.24*
0.80 ± 0.07*
68.84
SO
12.41 ± 0.51*
3.70 ± 0.45*
27.69 ± 1.56*
50.60 ± 1.08*
4.35 ± 0.22*
0.20 ± 0.04*
40.17
CSO camellia seed oil SO soybean oil a
Mean ± SD (n = 5)
* Significant different from the first group (p \ 0.05)
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percentage of linolenic acid, such as sesame oil, with the high linolenic acid content oils, such as soybean oil. However, the matrix effect is great when the linolenic acid content is low. Using the linolenic acid as the only adulteration parameter may influence the accuracy of this method. Therefore, a more accurate method was required.
200
AP
160
120
The Combination of C18:1, C18:2, and C18:3 Used as an Adulteration Parameter 80
In consideration of the high oleic acid content and low linoleic acid content in camellia seed oil as well as the opposite trends for soybean oil, we chose the ratio of oleic acid and linoleic acid as a discrimination parameter which had already been applied to detect the adulteration of olive oil with sunflower oil [22]. However, if the oleic to linoleic acid ratio was high but the total content of oleic and linoleic acid was really low, only considering this ratio would get an incorrect authentication result. To solve this problem, we introduced the total content of oleic and linoleic acid into the calculation. Based on the former method, we defined the adulteration parameter (AP) as follows: oleic AP ¼ linolenic 10 þ ðoleic þ linoleicÞ linoleic ð2Þ where oleic, linoleic and linolenic were the contents of oleic, linoleic and linolenic acid in a given pure or blended oil, respectively. The AP values of the pure and mixture oil samples were listed in Tables 1 and 2. The AP values of the pure camellia seed oils ranged from 176.39 to 210.85, which were much higher than those of the pure soybean oils ranging from 18.06 to 41.18. In contrast to the changed trend of linolenic acid, the AP values decreased rapidly when the adulteration levels increased (Fig. 4). The relationship between the adulteration levels and the AP values was expressed as the following equation: X2 ¼ 38:76Ln½ðAP 25:40Þ=173:26 R2 ¼ 0:999
ð3Þ
where X2 % was the adulteration level. In pure camellia seed oil, the ratio of C18:1 to C18:2 was above 9, and the total content of them was approximately 90 % as well as the content of C18:3 being lower than 0.4 %, we could know that the value of AP in pure camellia seed oil would be higher than 176. Thus, an AP value of 176 could be used as the criterion to differentiate pure and impure camellia seed oil. Based on the criterion, the detection limit of adulteration with soybean was approximately 5 %. The proposed method reduced the effect of the matrix. Moreover, the detection limit was lower than that of using only one parameter. This method
40 0
20
40
60
80
100
% soybean oil adulterated in camellia seed oil Fig. 4 The relationship between the AP values and the adulteration levels
can also be used to detect the adulteration of olive oil with some modifications. Comparison with Other Studies In the literature, the detection limit of adulteration of soybean oil in camellia seed oil was 5–25 % measured by attenuated total reflectance MIR and fiber optic diffuse reflectance NIR [24]. This method had low sensitivity and poor accuracy, the quantification of adulteration achieved by Partial least square regression needed many time-consuming data pretreatments. However, for our proposed method, just a couple of seconds were needed to accomplish the sample preparation step. What’s more, it has the advantages of simplicity, high sensitivity and efficiency. It was reported that the electronic nose has been used for the detection of camellia seed adulterated oil with maize oil. But the accuracy of prediction of adulteration was 83.6 % for camellia seed oil and 94.5 % for sesame oil, yet it could not be applied to predict adulteration of soybean oil [23]. However, our method could be used to detect the soybean oil as well as maize-oil-adulterated camellia seed oil, and the detection limit of adulteration was lower than those reported in the literature.
Conclusions Due to the high content of linolenic acid in soybean oil, we used it to determine the adulteration of camellia seed oil with soybean oil. According to the high content of oleic and linoleic acid and high ratio of oleic to linoleic acid in camellia seed oil, combined with linolenic acid, we used
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the parameter AP to differentiate between camellia seed oil and soybean oil. For the two parameters, AP was preferred. The detection limit of adulteration was as low as 5 % (the values were lower than 5 % in most cases), which was lower than those reported in the literature. This accurate and time-saving method may also be applied to determine the adulteration of olive oil. Acknowledgments This work was supported by the Key Discipline Construction Project of Shanghai Municipal Public Health (No. 12GWZX0401), and Shanghai Leading Academic Disciplines (No. S30109).
References 1. He SN, Guo Y (1982) The comprehensive utilization of camellia fruits. Am Camellia Yearb 37:104–107 2. Jiang YY, Wang LG, Ou MM (2008) Study on the antimicrobial effect of the camellia oil. J Anhui Agric sci 36(14):5913–5914 3. Rohman A, Che Man YB (2009) Analysis of cod-liver oil adulteration using Fourier transform infrared (FTIR) spectroscopy. J Am Oil Chem Soc 86:1149–1153 4. Sim SF, Ting W (2012) An automated approach for analysis of Fourier Transform Infrared (FTIR) spectra of edible oils. Talanta 88:537–543 5. Luca MD, Terouzi W, Kzaiber F (2011) Derivative FTIR spectroscopy for cluster analysis and classification. Food Chem 124:1113–1118 6. Rohman A, Che Man YB, Ismail A, Hashim P (2010) Application of FTIR spectroscopy for the determination of virgin coconut oil in binary mixtures with olive oil and palm oil. J Am Oil Chem Soc 87:601–606 7. Guo LX, Xu XM, Yuan JP, Wu CF, Wang JH (2010) Characterization and authentication of significant Chinese edible oilseed oils by stable carbon isotope analysis. J Am Oil Chem Soc 87:839–848 8. Seo HY, Ha J, Shin DB, Shim SL, No KM, Kim KS, Lee KB, Han SB (2010) Detection of corn oil in adulterated sesame oil by chromatography and carbon isotope analysis. J Am Oil Chem Soc 87:621–626 9. Wealey IJ, Barnes RJ, McGill AEJ (1995) Measurement of adulteration of olive oils by near infrared spectroscopy. J Am Oil Chem Soc 72:289–292 10. Li SF, Zhu XR, Zhang JH, Li GY, Su DL, Shan Y (2012) Authentication of pure camellia oil by using near infrared spectroscopy and pattern recognition techniques. J Food Sci 77(4): 374–380
123
J Am Oil Chem Soc (2013) 90:641–646 11. Lorenzo IM, Pavo´n JLP, Laespada MEF, Pinto CG, Cordero BM (2002) Detection of adulterants in olive oil by headspace–mass spectrometry. J Chromatogr A 945:221–230 12. Wu YJ, Zhang HL, Han JX, Wang B, Wang W, Ju XR, Chen Y (2011) PCR-CE-SSCP applied to detect cheap oil blended in olive oil. Eur Food Res Technol 233:313–324 13. Zhang HL, Wu YJ, Li YY, Wang B, Han JX, Ju XR, Chen Y (2012) PCR-CE-SSCP used to authenticate edible oils. Food Control 27:322–329 14. Gurdeniza G, Ozen B (2009) Detection of adulteration of extravirgin olive oil by chemometric analysis of mid-infrared spectral date. Food Chem 116:519–525 15. Zhang Q, Saleh ASM, Shen Q (2012) Discrimination of edible vegetable oil adulteration with used frying oil by low field nuclear magnetic resonance. Food Bioprocess Technol. doi: 10.1007/s11947-012-0826-5 16. Yang H, Irudayaraj J, Paradkar MM (2005) Discriminant analysis of edible oils and fats by FTIR, FT-NIR and FT-Raman spectroscopy. Food Chem 93:25–32 17. Berasategi I, Barriuso B, Ansorena D, Astiasara´n I (2012) Stability of avocado oil during heating: comparative study to olive oil. Food Chem 132:439–446 18. Christopoulou E, Lazaraki M, Komaitis M, Kaselimis K (2004) Effectiveness of determinations of fatty acids and triglycerides for the detection of adulteration of olive oils with vegetable oils. Food Chem 84:463–474 19. Park YW, Chang PS, Lee J (2010) Application of triacylglycerol and fatty acid analyses to discriminate blended sesame oil with soybean oil. Food Chem 123:377–383 20. Ramon A, Ramon A (2000) Authentication of vegetable oils by chromatographic techniques. J Chromatogr A 881:93–104 21. Al-Ismail KM, Alsaed AK, Ahmad R, Al-Dabbas M (2010) Detection of olive oil adulteration with some plant oils by GLC analysis of sterols using polar column. Food Chem 121: 1255–1259 22. Gamazo-Va´zquez J, Garcı´a-Falco´n MS, Simal-Ga´ndara J (2003) Control of contamination of olive oil by sunflower seed oil in bottling plants by GC–MS of fatty acid methyl esters. Food Control 14:463–467 23. Hai Z, Wang J (2006) Detection of adulteration in camellia seed oil and sesame oil using an electronic nose. Eur J Lipid Sci Technol 108:116–124 24. Wang L, Lee FSC, Wang XR, He Y (2006) Feasibility study of quantifying and discriminating soybean oil adulteration in camellia oils by attenuated total reflectance MIR and fiber optic diffuse reflectance NIR. Food Chem 95:529–536 25. Liao SJ, Ji DL, Tong HR (2005) Study on fatty acid composition and nutrition health protection function of the oil tea camellia seed oil. Cereals Oils 6:7–9