J. Agric. Food Chem. 2003, 51, 2687−2692
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Character Impact Odorants of Citrus Hallabong [(C. unshiu Marcov × C. sinensis Osbeck) × C. reticulata Blanco] Cold-Pressed Peel Oil HYANG-SOOK CHOI† Natural Sciences Research Center, College of Natural Science, Duksung Women’s University, 419 Ssangmun-Dong, Dobong-Gu, Seoul 132-714, Korea
The volatile components of Hallabong ([C. unshiu Marcov × C. sinensis Osbeck] × C. reticulata Blanco) cold-pressed peel oil were quantitatively and qualitatively determined by use of two internal standards with GC, GC-MS, and GC-olfactometry. According to instrumental analysis by GC and GC-MS, limonene (90.68%) was the most abundant compound, followed by sabinene (2.15%), myrcene (1.86%), and γ-terpinene (0.88%). Flavor dilution (FD) factors of the volatile flavor components from Hallabong peel oil were determined by aroma extract dilution analysis. Furthermore, relative flavor activity was investigated by means of FD factor and weight percent. The highest FD factors were found for citronellal and citronellyl acetate, and δ-murollene showed a higher relative flavor activity. Results of sniff testing of the original oil and its oxygenated fraction revealed that citronellal, cis-β-farnesene, and citronellyl acetate were regarded as the character impact odorants of Hallabong peel oil, and citronellal gave the most odor-active character of Hallabong aroma. KEYWORDS: Citrus Hallabong [(C. unshiu Marcov × C. sinensis Osbeck) × C. reticulata Blanco]; gas chromatography-olfactometry; aroma extract dilution analysis; character impact odorants; citronellal
INTRODUCTION
Fruits of the Citrus genus are important crops because of their nutritional and industrial uses. The genus Citrus consists of many species, all of which produce characteristic distinct flavor used in foods, perfumery, and cosmetics. In Korea, citrus fruits have long been used in traditional herbal medicine, especially for colds and coughs, and in bath products (1). Hallabong [(C. unshiu Marcov × C. sinensis Osbeck) × C. reticulata Blanco] is a new hybrid citrus crop in Korea and has been regarded as a citrus fruit with potential commercial value because of its attractive and pleasant aroma. The flesh of this fruit is juicy and has good taste with a sweet aroma. It matures in December in Jeju Province, an island off southeastern Korea. In 2001 the production of Hallabong in Korea was estimated to be 3901 tons. This fruit has a round shape with a neck, orange flesh and peel, and seedless flesh. Hallabong has a large diameter of 8-10 cm and an average weight of 350 g. This fruit has a sweet taste of 14-16 °Brix and an acids content of 1-1.2% (2). Citrus hybrids are so variable as the result of hybridization of many fine-quality mandarins and sweet oranges, and many of these varieties are now being used sucessfully for juice production and as fresh fruit (3). In view of the commercial value and wide applications of these hybrid fruits, every essential characteristic information, especially about the flavor quality of the essential oil of these fruits, should be presented. † Telephone +82-2-901-8163; fax +82-2-901-8372; e-mail hschoi@ center.duksung.ac.kr.
Gas chromatography-olfactometry (GC-O) of stepwisediluted aroma extracts is a systematic approach to estimate the contribution of the most odor-active compounds presented in the overall odor by sniffing the GC effluent. Aroma extract dilution analysis (AEDA) is used for the detection of potent odorants in foods and is useful for determining the odor activity, quality, and potency of food aroma (4-7). No attempt has been undertaken to identify the volatile components of Hallabong. In the present study, the quantitative and qualitative determination of Hallabong cold-pressed peel oil was carried out by GC, GC-MS, and GC-O, and their character impact odorants were elucidated by AEDA technique and sniffing test. MATERIALS AND METHODS Materials. Fresh Hallabong [(C. unshiu Marcov × C. sinensis Osbeck) × C. reticulata Blanco], which was harvested in December 2001, was provided by the Citrus Experiment Station Rural Development Administration, Jeju Province, Korea. The peel oil sample was prepared according to the cold-pressing method described by Choi and Sawamura (8) within 24 h of harvest. All of the fruits (∼5 kg) were sliced, and the mesocarp and albedo layers were peeled from the flavedo. The peel oils were extracted by hand-pressing the flavedo, and the peel oils were collected in brine solution on ice. The oil extract was centrifuged at 4000g for 15 min at 4 °C. The supernatant was dehydrated with anhydrous sodium sulfate at 5 °C for 24 h and filtered. The oil was stored at -25 °C until analyzed. The yield of cold-pressed oil was 1.02% of the flavedo by weight. Authentic chemicals for coinjection in GC and MS were obtained from reliable commercial sources as follows: Aldrich Chemical Co. (Milwaukee, WI), Sigma Chemical
10.1021/jf021069o CCC: $25.00 © 2003 American Chemical Society Published on Web 03/25/2003
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Choi
Table 1. Volatile Flavor Components Identified in the Cold-Pressed Peel Oil of Hallabong linear retention index no.
compound
DB-Wax
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74
ethyl acetate R-pinene camphene β-pinene sabinene myrcene limonene cis-β-ocimene γ-terpinene p-cymene terpinolene tridecane tetradecane cis-linalool furan oxide (+)-cis-limonene oxide (−)-R-cubebene (+)-trans-limonene oxide menthone trans-linalool furan oxide citronellalg pentadecane decanal β-cubebene linalool octanol linalyl acetate nonyl acetate β-elemene β-caryophyllene terpinen-4-ol l-menthol γ-elemene cis-β-farneseneg citronellyl acetateg trans-β-farnesene R-humulene δ-muurolene decyl acetate neral terpinyl acetate R-terpineol dodecanal germacrene D valencene bicyclogermacrene cis-linalool pyran oxide trans−2-undecenal citronellol sesquiphellandrene cumin aldehyde perilla aldehyde octadecane methyl laurate tridecanal p-mentha-1-en-9-yl acetate isopiperitone cis-carveol geraniol trans-2-dodecenal trans-carveol perilla alcohol dehydrocarveol p-mentha-1-en-9-ol tetradecenal caryophyllene oxide cis-nerolidol methyl tetradecanoate trans-dodec-2-enol trans-nerolidol globulol octanoic acid elemol viridiflorol cedrenol
898 1034 1077 1124 1134 1168 1234 1245 1262 1282 1297 1312 1399 1453 1458 1463 1470 1474 1478 1485 1504 1538 1546 1554 1566 1569 1585 1595 1608 1616 1626 1636 1648 1663 1674 1680 1684 1691 1695 1700 1711 1718 1722 1726 1738 1750 1761 1771 1780 1789 1797 1805 1813 1824 1834 1841 1846 1862 1872 1876 1892 1941 1945 1989 1999 2010 2034 2040 2054 2061 2083 2089 2102 2113
DB-5 933 953 981 973 991 1039 1043 1059 1027 1084 1291 1116 1070 1138 1345 1139 1172 1161 1229 1018 1098 1072 1261 1302 1393 1428 1178
1357 1444 1408 1235 1185 1401 1490
1435 1149 1271 1503 1230 1462
1486 1573 1565 1539 1547 1604
peak % (w/w)
identification
refa
trb 0.53 0.01 0.10 2.15 1.86 90.68 0.16 0.88 0.02 0.11 0.01 0.06 tr 0.01 tr 0.02 0.03 0.02 0.19 0.50 tr 0.02 0.47 0.01 tr 0.01 0.01 0.04 tr tr 0.01 0.03 0.04 0.01 tr tr tr tr 0.05 0.12 0.01 0.03 0.04 0.11 0.81 0.03 0.15 tr 0.06 tr 0.01 0.04 tr 0.01 0.01 0.01 0.01 tr tr 0.01 tr tr tr 0.01 tr tr 0.02 0.01 tr 0.01 0.01 tr 0.01
RI,c MS,d GC-Oe RI, MS, Co-GC,f GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, Co-GC, GC-O RI, MS, Co-GC RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, GC-O RI, MS, Co-GC, GC-O RI, MS, GC-O RI, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, GC-O RI, MS, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC RI, MS, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, GC-O RI, MS, Co-GC, GC-O RI, MS RI, MS RI, MS, Co-GC, GC-O RI, MS, GC-O RI, MS, Co-GC, GC-O
18 18, 19 18, 19 18, 19 18, 19 18, 19 18, 19 18, 19 18, 19 18, 19 18, 19 20, 21 18, 19, 21 19, 21 18, 19, 21 19−21 18, 19, 21 18, 21 18, 19, 21 18, 20, 21 18, 20, 21 18−21 18−21 18−21 18−21 18−21 18−21 18−21 18−21 18−21 21 19, 20 19−21 18, 20, 21 19−21 18−21 18, 21 18, 20, 21 18, 19, 21 18, 21 18−21 18−21 18−21 18, 21 18, 21 21 21 18, 19, 21 18−21 18, 19, 21 19−21 17, 21 21 19−21 18, 21 20, 21 18, 19, 21 18−21 21 19, 21 18, 21 21 21 21 21 19, 20 21 19, 20 18 19 21 19, 20 19, 20
odor description
FD factor (3n)
sweet, green sweet, fruity sweet, green sweet sweet, fruity green, citrus-like citrus-like herbaceous, fruity, sweet fruity, sweet fruity citrus-like, fruity mild herbaceous, sweet sweet
5 1 3 4 6 6 4 5 6 3 2 1 1
mild waxy, woody mild green fresh, green fresh, green, fruity citrus peel-like mild green herbaceous fruity, citrus-like fruity, sweet, green green sweet, fruity fruity, sweet waxy, herbaceous fruity, sweet sweet, herbaceous fresh, green, cool green, oily green, citrus-like citrus-like, oily oily, fruity, citrus-like oily, fruity oily oily, fruity oily, citrus-like waxy oily, fruity oily, herbaceous oily, green oily, green green green, citrus-like sweet, green sweet, citrus-like sweet, fruity, herbaceous green sweet, herbaceous sweet, fruity sweet, fruity sweet, fruity herbaceous, fruity sweet, fruity citrus-like, fruity sweet citrus-like, oily green, oily
1 4 4 5 7 1 4 5 5 3 3 5 5 5 4 4 3 5 7 6 4 5 3 3 6 5 5 3 3 3 3 3 5 4 3 2 3 1 2 2 1 1 3 1 2
oily, herbaceous fruity, herbaceous
1 2
sweet, fruity waxy waxy oily waxy
1 2 1 4 4
green sweet, green fruity
1 1 2
Character Impact Odorants of Citrus Hallabong Peel Oil
J. Agric. Food Chem., Vol. 51, No. 9, 2003
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Table 1 (Continued) linear retention index no.
compound
DB-Wax
75 76 77 78 79 80 81 82 83 84 85 86 87 88
spathulenol eugenol γ-eudesmol nonanoic acid R-cadinol β-eudesmol trans,trans-farnesyl acetate cinnamyl alcohol limonenediol trans,trans-farnesol nerol oxide octadecanal undecanoic acid undecanal hydrocarbons aliphatics (4)h monoterpenes (10) sesquiterpenes (13) aldehydes aliphatics (8) terpenes (4) alcohols aliphatics (2) monoterpenes (14) sesquiterpenes (11) ketones (2) esters (10) oxides and epoxides (7) acids (3)
2129 2175 2185 2202 2211 2246 2283 2300 2334 2371 2385 2400 2407 2444
total
DB-5 1351
1654 1312 1722 1490
peak % (w/w)
identification
refa
odor description
FD factor (3n)
tr tr 0.02 tr tr 0.01 tr 0.01 tr tr tr tr tr 0.01
RI, MS, GC-O RI, MS, Co-GC, GC-O RI, MS, GC-O RI, MS, Co-GC, GC-O RI, MS, GC-O RI, MS, Co-GC, GC-O RI, MS, GC-O RI, MS, Co-GC, GC-O RI, MS, GC-O RI, MS, Co-GC, GC-O RI, MS, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O RI, MS, Co-GC, GC-O
19 18 18, 19 18 20 18, 19 19, 20 19, 20 21 19 21 20 20 20
fruity, herbaceous herbaceous sweet, waxy green green, waxy, woody green, woody oily, waxy oily green, waxy oily oily oily oily oily
2 1 2 2 2 3 3 4 3 4 3 3 3 3
0.58 96.5 0.30 0.05 0.25 0.03 0.78 0.06 0.04 0.15 0.87 0.01 99.62
a Reference number where identified earlier. b Trace,
