A Comparison of Volatile Components of Setomi with Its Parent Cultivars

Biosci. Biotechnol. Biochem., 74 (3), 659–662, 2010 Note A Comparison of Volatile Components of Setomi with Its Parent Cultivars

y Yoshihiko AKAKABE,1; Aya KUSUNOKI,1 Rina TANAKA,1 and Yasuhiko KANETSUNE2

1Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University, 1677-1 Yoshida, Yamaguchi 753-8515, Japan 2Yamaguchi Prefectural Agriculture and Forestry Research Center, 1209-1 Higashiagenosyou, Suohoshima-cho, Yamaguchi 742-2805, Japan

Received October 2, 2009; Accepted December 9, 2009; Online Publication, March 7, 2010 [doi:10.1271/bbb.90722]

The citrus fruit Setomi is a hybrid of Yoshiura Kiyomi is the first tangor cultivated in Japan, and is ponkan (Citrus reticulate Blanco) and Kiyomi (Citrus known as a good parent cultivar for Shiranui, Setoka, unshiu Mrcov. Â Citrus sinensis Osbeck). The essential and Harumi. The fruit of Kiyomi is very juicy and has a oils from the peel of Setomi and its parent cultivars were slightly sour taste. It has been evaluated that the fruit of obtained by a simultaneous distillation extraction tech- Setomi has a mellow flavor, but there are no reports nique. Comparing the essential oils of Setomi and its concerning the aroma volatile components in Setomi parent cultivars, it was found that the oil in the peel of fruits. The aim of this study was to identify the volatile Setomi consisted of characteristic aroma components components in the peel of Setomi by GC-MS and to from each parent cultivar. The principal component compare the odor with those of Yoshiura ponkan and analysis of data, obtained with an electronic nose, Kiyomi as parent cultivars with an electronic nose. indicated that the odor quality of Setomi was different Setomi, Yoshiura ponkan, and Kiyomi fruits were from those of the parent cultivars. gifts of the Yamaguchi Prefectural Agriculture and Forestry Research Center from January to March 2007, Key words: citrus fruit; volatile component; electronic and from February to March 2008. The peels were nose stored at 25 C until use. The essential oil was prepared by the simultaneous distillation extraction Many citrus plantations are found all over the world, technique at atmospheric pressure. The peel of Setomi and the essential oils from the fruits are widely utilized (100 g) was homogenized with distilled water (200 ml), in foods and beverages, and as fragrances in cosmetics. and the homogenate was immediately subjected to There have been many reports concerning volatile simultaneous distillation extraction for 2 h with pen- components in citrus fruits such as the orange,1) grape- tane-dichloromethane (2:1 v/v, 150 ml) as the extraction fruit,2) and kumquat.3) Usually, citrus fruits have solvent. Tridecane (100 mg) in dichloromethane (1 ml) characteristic sweet-sour odors, and the odors are was added as an internal standard. The extract was dried tempered by a complex blend of volatile components, over anhydrous Na2SO4 and concentrated (442– which derive from the various parent cultivars. Thus the 293 mmHg, 40 C) to give an essential oil (1.77% amounts and composition patterns of the volatile yield). The essential oils were kept under N2 at 20 C components of citrus fruits are important indicators in until analyzed. This procedure was carried out 3 times. identifying similarities and classifying the chemotypes By essentially the same procedure, Yoshiura ponkan and of citrus fruits, but there have been few reports Kiyomi essential oils were obtained in 1.79% and 1.55% concerning the compositions of volatile components yield respectively. The aromas of the essential oils were between a cultivar and its parent cultivars in citrus fruits. described as plain, sour, fresh, fruity, grassy in Setomi, We have reported that the essential oil in the peel of as fresh, plain, fruity in Yoshiura ponkan, and as grassy, Ohshima no. 1, which is a hybrid of Yoshiura ponkan spicy, pungent in Kiyomi by panelists. (Citrus reticulate Blanco) and Miyauchi iyokan (Citrus The volatile components of the essential oils were iyo Hort. ex Tanaka), consisted of characteristic aroma analyzed and identified using a Shimadzu QP-5050 components from each parent cultivar.4) We have also GC-MS (Shimadzu, Kyoto, Japan) equipped with a found that it is important to compare the components of capillary column of DB-WAX (0.25 mm i.d. 60 m; a cultivar with its parent cultivars. film thickness, 0.25 mm). The oven temperature was The citrus fruit Setomi is a hybrid of Yoshiura ponkan programmed from 50 C to 230 C at a rate of 2 C/min. and Kiyomi (Citrus unshiu Mrcov. Citrus sinensis The injection port and ionizing source were kept at Osbeck). Yoshiura ponkan was chosen in a selection of 240 C and 230 C respectively. Helium was the carrier the finest cultivars, along with ponkan, in Ohshima, gas, at the flow rate of 1.5 ml/min. Essential oil at 1 ml Yamaguchi Prefecture, Japan. It has been evaluated that was injected into the GC-MS, with the split ratio of the the fruit of Yoshiura ponkan is sweet as compared to injector at 1:50. Retention indexes were determined for other citrus fruits, while it is not very juicy. Kiyomi is all constituents using a homologous series of n-alkanes a tangor hybridized between Satsuma mandarin (C. (C9 to C26). Individual components were identified by unshiu Mrcov) and Trobita orange (C. sinensis Osbeck). comparison of retention indexes and mass spectra with

y To whom correspondence should be addressed. Tel: +81-83-933-5851; Fax: +81-83-933-5820; E-mail: [email protected] 660 Y. AKAKABE et al. Table 1. Volatile Components of the Peels of Setomi and Its Parent Cultivars

mg/100 g peela b d RI Compound Yoshiura Identification Setomi SDc SD Kiyomi SD ponkan 1018 -Pinene 7.70 0.64 8.79 2.55 2.65 0.06 1 1054 -Thujenee 2.16 0.15 2.22 0.28 1.69 0.46 2 1104 -Pinene 5.03 0.36 5.21 0.59 — — 1 1117 Sabinenee 1.11 0.06 4.23 0.42 — — 2 1159 Myrcene 17.04 1.49 27.05 3.44 14.48 0.54 1 1174 -Terpinene 1.18 0.13 1.50 0.17 1 1203 Limonene 723.13 77.13 1176.12 126.06 704.72 30.75 1 1207 -Phellandrenee 2.21 0.22 3.99 0.63 2.14 0.10 2 1214 (E)-2-Hexenal — — — — 0.36 — 1 1242 -Terpinene 59.68 5.67 77.05 9.34 0.25 0.02 1 1247 (E)--Ocimene 3.47 0.22 1.04 0.04 0.54 0.10 1 1264 p-Cymene 14.62 0.81 1.39 0.26 — — 1 1277 Terpinolene 3.28 0.28 3.67 0.56 — — 1 1284 Octanal 1.27 0.17 4.49 0.98 1.37 0.20 1 1300 IS (Tridecane) 1388 Nonanal 0.69 0.02 0.46 0.07 0.60 0.09 1 1430 Dehydro-p-cymenee 0.86 0.07 — — — — 2 1465 -Elemenee 0.43 0.08 — — — — 2 1471 Citronellale — — 1.00 0.31 — — 2 1472 Octyl acetate — — — — 0.28 — 1 1493 Decanal 4.59 0.13 3.88 0.44 2.00 0.12 1 1545 Linalool 1.88 0.10 15.86 2.84 1.39 0.17 1 1585 Thymyl ethyl ether — — 0.54 0.07 — — 1 1590 -Caryophyllene — — — — 0.18 0.02 1 1598 4-Terpineol 0.90 0.07 1.53 0.22 0.57 0.12 1 1661 (E)--Farnesene 1.48 0.07 — — 0.26 — 1 1675 Neral — — — — 0.30 0.01 1 1693 -Terpineol 1.52 0.06 2.84 0.50 1.04 0.04 1 1702 GermacreneD 0.79 0.12 — — — — 1 1703 Dodecanal 0.41 0.01 0.47 0.03 0.19 — 1 1712 Valencene — — — — 3.74 0.25 1 1721 Neryl acetate — — — — 1.55 0.10 1 1725 Geranial — — — — 0.35 0.07 1 1727 (þ)-Carvone 0.45 — — — — — 1 1743 (E,E)--Farnesene 0.81 0.06 — — 0.19 — 1 1752 -Cadinenee — — — — 0.41 0.07 2 1762 Citronellol — — 0.45 0.11 — — 1 1775 Perillale — — 0.36 0.00 0.18 0.01 2 1822 Germacrene Be 0.62 0.09 — — — — 2 1992 Perillole — — — — 0.20 — 2 2176 Thymol — — 0.37 0.04 — — 1 2222 -Sinensale 1.58 0.10 — — 0.29 0.07 2 2230 Unknown — — — — 0.20 — 2236 Unknown — — — — 0.60 0.09 2323 -Sinensale 1.80 0.05 0.43 0.01 0.19 — 2

aIndividual components were quantified from peak areas by comparison with the internal standard (tridecane). bRetention indexes. cStandard deviation of three samples. d1, comparison with retention indexes and mass spectra of authentic standards by co-injection; 2, comparison with retention indexes and mass spectra similar to mass libraries. eTentatively identified. those of authentic standards, and were quantified from The classification into functional groups is shown in peak areas by comparison with the internal standard. Table 2. As shown in Table 1, a total of 28 volatile The odor evaluations were performed with an elec- components were identified in the essential oil of the tronic nose (Fragrance and Flavor Analyzer, FF2A, peel of Setomi by GC-MS. The components in the oil Shimadzu, Kyoto, Japan) using the oils. The sensor included 13 monoterpenes (97.75%), five sesquiterpenes array was composed of 10 metal-oxide semiconductor (0.48%), four monoterpene oxides (0.55%), two sesqui- types. A paper containing the oil (10 mg), as described terpene oxides (0.39%), and four aldehydes (0.83%). The above, was put into a sample bag with a volume of 2 essential oils of the parent cultivars, Yoshiura ponkan liters. Then the bag was closed and allowed to and Kiyomi, were also identified, as 25 and 30 equilibrate the headspace for 1 h. Then the headspace components respectively. The components in the essen- gas was pumped over the sensors of the electronic nose. tial oil of Yoshiura ponkan included 12 monoterpenes The volatile components in the essential oil of the peel (97.57%), eight monoterpene oxides (1.71%), one ses- of Setomi and its parent cultivars are listed in Table 1. quiterpene oxide (0.03%), and four aldehydes (0.69%). Volatile Components of Setomi 661 Table 2. Classification of Functional Groups of Volatile Components from the Peels of Setomi and Its Parent Cultivars

Setomi Yoshiura ponkan Kiyomi Functional groups No. mg/100 g peela (%) No. mg/100 g peel (%) No. mg/100 g peel (%) Monoterpenes 13 841.47 (97.75) 12 1312.26 (97.57) 7 726.47 (97.79) Sesquiterpenes 5 4.13 (0.48) — — 5 4.78 (0.64) Monoterpene oxides 4 4.75 (0.55) 8 22.95 (1.71) 8 5.58 (0.75) Sesquiterpene oxides 2 3.38 (0.39) 1 0.43 (0.03) 2 0.48 (0.06) Aldehydes 4 7.13 (0.83) 4 9.3 (0.69) 5 4.52 (0.61) Ester — — — — 1 0.28 (0.04) Unknown — — — — 2 0.8 (0.11)

aIndividual components were quantified from peak areas by comparison with the internal standard (tridecane).

-Thujene, thymyl ethyl ether, dodecanal, citronellol, and -sinensal were detected for the first time in the oil of 2.00 Setomi Yoshiura ponkan. However, the total composition pattern Yoshiura ponkan of the volatile components in Yoshiura ponkan was very Kiyomi 4) similar to the previous data. In a similar way, those 1.00 of Kiyomi included seven monoterpenes (97.79%), five sesquiterpenes (0.64%), eight monoterpene oxides (0.75%), two sesquiterpene oxides (0.06%), five alde- 0.00 hydes (0.61%), and one ester (0.04%). Among these, limonene was the major volatile component in the oil of PC2 (27.8%) Setomi, and comprised 85.94% of the total aroma components. However, the proportion of limonene in -1.00 the oil of Setomi was lower than in Kiyomi (97.01%) or Yoshiura ponkan (89.63%). Monoterpenes such as - pinene, -thujene, myrcene, -phellandrene, -terpinene, -2.00 and (E)--ocimene were detected in the three cultivars, and the amounts and the composition pattern of the -2.00 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50 volatile components in Setomi were similar to Yoshiura PC1 (64.2%) ponkan. -Pinene, sabinene, -terpinene, p-cymene, and terpinolene were detected only in these cultivars. Gen- Fig. 1. Principal Component Analysis of the Data Obtained with an erally, monoterpenes have green, citrus, herbal, and fresh Electronic Nose on Essential Oils from the Peels of Setomi and Its odors, and these odors appeared to contribute to the Parent Cultivars. aroma quality of Setomi and Yoshiura ponkan. Alde- hydes such as octanal, nonanal, decanal, and dodecanal sweet, fruity, and citrusy odors, and (E)--farnesene has were detected in the three cultivars, although (E)-2- citrusy and floral odors5)), indicating that these com- hexenal was detected only in Kiyomi. Among these, the pounds contribute to the aroma quality of Setomi. amount of octanal was higher in Yoshiura ponkan, while Valencene, which has a burnt and smoky odor,8) appears that of decanal was higher in Setomi. Dodecanal to be a key aroma in Kiyomi. Although monoterpene occurred in higher amounts in Setomi and Yoshiura alcohols such as linalool, 4-terpineol, and -terpineol ponkan. Because these aldehydes have low thresholds, were detected in the three cultivars, the amounts were the composition of the aldehydes appears to be key to the similar between Setomi and Kiyomi. Linalool has floral, aroma quality of each citrus fruit. For example, octanal citrusy, and sweet odors at a low threshold, suggesting has sweet and floral odors, and decanal has sour and that alcohol is important for each citrus aroma. Among acidic odors. These compounds have been identified as a sesquiterpene oxides, -sinensal and -sinensal, which ponkan-like odor.5) Similarly, nonanal has sweet and have a green, grassy aroma,5) were detected in Setomi in citrusy odors, and dodecanal has sour and grassy odors.5) higher amounts. These components can contribute to the Setomi inherited these aldehydes from both parent aroma quality of Setomi, because it has been found to be cultivars, indicating that these compounds appear to present in many sweet orange-peel oils9,10) and to contribute to the aroma quality of Setomi. Sesquiterpenes contribute to the aroma of citrus fruits. Based on these were predominantly detected in Setomi and Kiyomi, and results, the aroma of Setomi consisted not only of in particular, (E)--farnesene and (E,E)--farnesene inherited compounds from both parent cultivars’ compo- were detected only in these cultivars. -Elemene, nents (such as citrusy and green odors in monoterpenes, germacrene D, and germacrene B were found in Setomi, sweet, citrusy, and sour odors in aldehydes), but also of whereas valencene and -cadinene were found in predominant constituents (such as sweet and fruity odors Kiyomi. Valencene was found in large amounts in in -elemene, citrusy and floral odor in (E)--farnesene, Kiyomi, which is known for a major sesquiterpene in and grassy and green odors in - and -sinensal). orange, and is used as an indicator of good quality in Under some high-temperature or acidic conditions, orange oil.6) Compared aroma types of sesquiterpenes, terpenes, such as limonene and linalool, can degrade to germacrene D, -cadinene, and (E,E)--farnesene have other terpenes, such as 4-terpinenol and -terpineol. It is green, grassy, and herbal odors.5,7) Particularly, some suggested that these terpenes are a significant off-flavor sesquiterpenes have characteristic odors (-elemene has in citrus juices, but the amounts of 4-terpinenol and 662 Y. AKAKABE et al. -terpineol did not increase under the simultaneous Sports, Science, and Technology of Japan and from the distillation extraction method according to GC-MS Japan Food Chemical Research Foundation. We thank analysis. Hence this method produced a desirable aroma Hasegawa Co. (Kanagawa, Japan) and Taiyo Co. and made the essential oils fragrant and valuable. (Osaka, Japan) for donating authentic standards. Principal component analysis of the data obtained with the electronic nose indicated that the odor of Setomi References showed displacement in a positive direction and a 1) Mohamed AF, Brahim YM, Jacqueline S, and Farid C, downward displacement as compared with those of J. Chromatogr. A, 1112, 121–126 (2006). Yoshiura ponkan and Kiyomi in PC1. Furthermore, the 2) Njoroge SM, Koaze H, Karanja PN, and Sawamura M, J. Agric. oils of Setomi showed displacement in an upward direc- Food Chem., 53, 9790–9794 (2005). tion and a negative one in PC2. By principal component 3) Choi H-S, J. Agric. Food Chem., 53, 1642–1647 (2005). analysis, it was found that the odor quality of Setomi was 4) Akakabe Y, Kusunoki A, Ikeda Y, and Tanaka M, Biosci. Biotechnol. Biochem., 72, 1969–1972 (2008). different from those of the parent cultivars (Fig. 1). 5) Sawamura M, Minh Tu NT, Onishi Y, Ogawa E, and Choi HS, Judging from the GC-MS analysis and the electronic Biosci. Biotechnol. Biochem., 68, 1690–1697 (2004). nose analysis, we found that the composition pattern and 6) Elston A, Lin J, and Rouseff R, Flavour Fragr. J., 20, 381–386 the amounts of volatile components in Setomi appeared (2005). to form an original aroma quality as compared with the 7) Choi HS, J. Agric. Food Chem., 51, 2687–2692 (2003). parent cultivars. 8) Lan Phi NT, Nishiyama C, Choi HS, and Sawamura M, Biosci. Biotechnol. Biochem., 70, 1832–1838 (2006). 9) Chisholm MG, Jell JA, and Cass JrDM, Flavour Fragr. J., 18, Acknowledgments 275–281 (2003). 10) Mitiku SB, Sawamura M, Itoh T, and Ukeda H, Flavour Fragr. This work was supported in part by Grants-in-Aid J., 15, 240–244 (2000). (no. 19380050) from the Ministry of Education, Culture,