Agric. Chem. Biotechnol. 46(4), 152-155 (2003)
Article
Identification of Volatile Compounds in Structured Lipid of Safflower Oil using Electronic Nose and Solid Phase Microextraction Gas
Chromatograph-Mass Spectrometry
Jung-Ah Shin, Jong-Ho Lee1 and Ki-Teak Lee*
Department of Food Science and Technology, Chungnam National University, 220 Gung-Dong, Yusung-Gu, Taejon 305-764, Republic of Korea
1Department of Food and Nutrition, Yonsei University, 134 Shinchon-Dong, Sudaemun-Gu, Seoul 120-749, Republic of Korea Received October 23, 2003; Accepted December 1, 2003
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Key words: Structured lipids, safflower oil, flavor, electronic nose, SPME-GC/MS.
Recently, structured lipids (SLs) have been extensively studied for their applications in food industry.1-3) SLs are lipids in which the positions and the composition of fatty acids are altered by chemical or enzymatic esterification reaction. Even though several studies on the physicochemical properties of SLs have been reported, very little is known about their flavor characteristics. In our experiment, conjugated linoleic acids (CLAs) showing physiological benefits4-6) were incorporated into safflower oil to produce SL-safflower oil. CLAs refer to a series of positional and geometric isomers of LA, mainly composed of 9c, 11t-CLA and 10t, 12c-CLA with conjugated double bonds. An electronic nose and solid phase microextraction (SPME) gas chromatograph (GC) with mass spectrometry (MS) applied to compare the flavors of safflower and SL-safflower oils. Volatile flavor analysis by electronic nose is a quick and simple method, which requires no pretreatment, and, thus, is used in proportion to an increasing number of industry for environmental monitoring, product development and quality control of food. Various applications of electronic nose such as lipid oxidation of soybean oil7), and habitat discrimination for agricultural product8) have been reported. The volatiles of vegetable oil could be analyzed using the new, simple, solventless and rapid technology of SPME combined with GC for separation and MS for identification. The objectives of this study were to discriminate and identify the principal volatile compounds of safflower and SL-safflower oils by electronic nose system and SPME-GC/MS.
Materials and Methods
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Deacidification. SL-safflower oil was produced to incorporate CLA into safflower oil by lipase-catalyzed reaction, followed by alkali refining. Deacidification to remove free fatty acid was performed with 0.5 N KOH solutions (20% ethanol, 120 ml) as described by Lee.9) Obtained SL-safflower oil was isolated from the solvent by a rotary evaporator.
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Electronic nose analysis for flavor profiles. To determine the organoleptic characteristics, flavor patterns of safflower and SL-safflower oils were analyzed using Fox
*Corresponding author
Phone: +82-42-821-6729; Fax: +82-42-822-6729 E-mail: [email protected]
Identification of Volatile Compounds of Structured Lipid 153
3000 Electronic Nose (Alpha M.O.S., SA, France) equipped with a metal oxide sensor array (total 12 sensors) and an auto- sampler. Five grams each SL-safflower and safflower oils were placed separately in a 20-ml vials. The vials were then sealed with a silicon/PTFE septum and aluminum hole-cap.
Eight replications of each sample were analyzed three times by electronic nose. An air conditioning unit (air flow:
150 ml · in−1) was used to maintain the air (99.995% pure) at 20% constant relative humidity. Each sample vial was incubated in a heating chamber at 70oC with agitation (600 rpm) for 30 min. Syringe temperature was set at 75oC, and headspace of the samples (2500µl) was injected into the sensors automatically. Acquisition and delay times of the sample were 120 s and 30 min, respectively. After acquisition, a data processing software was used to collect raw data as the response of sensors. From the data obtained, principal component analysis (PCA) was conducted.
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Results and Discussion
Table 1 shows the fatty acid composition of safflower oil and the incorporation level of CLA into SL-safflower oil. The
most abundant fatty acid in safflower oil was linoleic acid (C18:2, 74.89 mol%). In SL-safflower oil, 26.45% of CLA were incorporated into safflower oil. After enzymatic modification, most of the linoleic acids were substituted with CLA in the fatty acid composition of SL-safflower oil during the incubation period.
Electronic nose was used to differentiate the aroma intensities ((∆R)/R0) of safflower and SL-safflower oils.
Principal component analysis (PCA), which enables the composite aroma information obtained by sensors to be classified in separate ellipses for discrimination, was carried out on the oil samples, and composite aroma information was plotted (Fig. 1). The first principal component contained most of the information (84.91%), while the second principal component comprised slight amount of information (14.04%).
PCA results revealed a clear discrimination between aroma of safflower oil and that of SL-safflower oil, an indication that the processing of SL production affected the flavor of
Table 1. Fatty acid composition (mol%) of safflower and modified SL-safflower oils
Fatty acids (mol%)a Safflower oil SL-safflower oil
C 16:0 ± ±
C 18:0 ± ±0.
C 18:1 ± ±
C 18:2 ± ±
C 18:3 ±±
CLA - b ±
aValues are means of two determinations with standard deviations.
bNot detected.
Fig. 1. Principal component analysis (PCA) profile of flavor intensities of safflower and SL-safflower oils. (A) ù, SL-saf- flower oil; (B) ø, safflower oil
Table 2. Responses of electronic nose on safflower and SL- safflower oils
Sensor model Response of each sensora Safflower oil SL-safflower oil
SY/LG 0.003906b 0.007113a
SY/G -0.01363a -0.04942b
SY/AA -0.00638a -0.02301b
SY/Gh -0.00897a -0.03022b
SY/gCTl -0.00655a -0.02467b
SY/gCT -0.00658a -0.0227b
T30/1 0.065547a 0.062425a
P10/1 0.038457a 0.040577a
P10/2 0.026571a 0.027046a
P40/1 0.035191a 0.035073a
T70/2 0.053762a 0.053695a
PA2 0.125783a 0.111735b
aMeans in the same row with different superscripts are significantly different at p<0.05 by MANOVA.
154 Jung-Ah Shin et al.
safflower oil. When Multivariate Analysis of Variance (MANOVA) and Student-Newman-Keul’s were applied, 7 out of 12 sensors differentiated the aroma intensities of safflower and SL-safflower oils (p < 0.05, Table 2).
Major volatile compounds, identified by SPME-GC/MS, having high sensitivity in both safflower and SL-safflower oils are shown in Table 3. The DVB/PDMS fiber has successfully been used for the isolation of volatile compounds in lipids.12) Identified headspace volatiles of safflower oil were decanol, octanol, (E)-2-heptenal, and hexanal. However, the amounts of these compounds were slight compared to those in SL- safflower oil (Table 3). In SL-safflower oil, off-flavor compoundsof polyunsaturated fatty acids13) including (E)-2- heptenal, 5-octen-1-ol, 3,5-octadien-2-ol, 2,4-pentadien-1-ol, (E,E)-2,4-nonadienal, and (E,E)-2,4-decadienal were detected. Aldehydes, ketones, acids, and alcohols have been reported from the corresponding hydroperoxides in the secondary oxidation products of lipids. Because aldehydes and alcohols have very low threshold values, they are expected to have a strong influence on the flavor. Therefore, oxidative compounds in SL-safflower oil are responsible for flavor degradation, and the process to decrease oxidation should be carefully considered during the SL production.
Acknowledgments. This work was supported by the grant (No. R05-2002-000-00033) from the Basic Research Program of the Korea Science & Engineering Foundation.
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Peak No.
Safflower oil
Peak No.
SL-safflower oil
RT Volatile compounds Relative area
Peak area (%)
RT Volatile compounds Relative area
Peak area (%)
1 3.65 Hexanal 28 11.17 1 3.61 Hexanal 155 5.95
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Total 254 100 Total 2606 100
aRelative peak areas are calculated using 1.2 mg of nonadecane (IS). Values are the means of two determinations.
Fig. 2. Chromatograms of headspace volatiles in safflower and SL-safflower oils by SPME-GC/MS. (A) safflower oil;
(B) SL-safflower oil
Identification of Volatile Compounds of Structured Lipid 155
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