Aroma characteristics of dried citrus fruits - blended green tea

Sung Hee Choi , Ju Yeon Jeon and Ji Won Jang

Dept. of Food Science and Nutrition, Dongeui University, 995 Eomgwangno, Busanjin-gu, Busan 614-714, Korea Correspondent email: [email protected]

Summary The purpose of this study was to characterize the aroma of green tea blended with the dried flesh and rinds from citrus fruits. Two kinds of citrus fruits (mandarin orange and citron) were used to infuse the teas with aromatic flavors. This process turned unflavored tea into special tea with a good color and preferred flavor. Aroma compounds were extracted by the SDE method. The concentrated aroma extracts were analyzed and identified by GC and GC-MS. The main aroma components of the green tea blended with mandarin orange were limonene (72.18%), (Z)-ocimene (8.40%), phenyl acetaldehyde (6.23%), γ-terpinene (5.21%), β-elemene (1.82%) and linalool (1.01%). The main aroma components of the green tea blended with citron were limonene (74.07%), γ-terpinene (10.07%), (Z)-ocimene (5.55%), (E)-ocimene (4.50%), linalool (1.03%) and β-mycrene (0.90%). The aroma of green tea blended with dried citrus fruits were mainly mono - and sesquiterpenic compounds.

Introduction The use of green tea of middle or low grade does not have an influence on health benefits, but has an influence on flavor. Therefore, two kinds of dried citrus fruits (mandarin orange and citron) respectively were added to green tea of middle grade to make a new special tea having good color, preferred flavor and functional properties.

Materials and methods Materials Mandarin orange grown in Je-ju Island in Korea was purchased from a local market. Citron grown in Kyung-nam in Korea was purchased from a local market. The peel and flesh from the two kinds of citrus fruits were washed, separated and sliced, and mandarin orange was dried at 50ºC for 14hr and citron was dried at 50ºC for 24hr, and stored at -10ºC in a refrigerator before further experiments. Korean steamed green tea was purchased from Kwang-ju, Jeon-nam (2009, product). Preparation of flavor concentrates The flavor concentrates from 50g of the materials were isolated by modified Likens and Nickerson method, using a simultaneous distillation and extraction apparatus. The steam distillation and extraction (water : diethyl ether = 1000 : 50ml) was continued for 1.5hr. The extract was dried over anhydrous sodium sulfate and the solvent was removed by the distillation of diethyl ether. Instrumental methods and identification of flavor concentrates The concentrated extract was analyzed and identified by GC and GC-MS. A gas chromatograph (Shimadzu model 17A, Kyoto, Japan) equipped with FID and a HP-5MS fused silica capillary column (30m × 0.25mm i.d. × 0.25μm film thickness) was used. The oven temperature was held at 50ºC for 8min and then programmed to 220ºC by 2ºC/min. Nitrogen was used as a carrier gas and the flow rate was 1ml/min. The GC-MS system consisted of a Hewlett - Packard 6890 GC/5973 MS (ionization voltage : 70eV, Palo Alto, CA, USA). The GC conditions were the same as those for corresponding GC analysis, except that helium was used as the carrier gas. Components were identified tentatively by matching the mass spectra with those of reference compounds in the date system of Wiley library. Identifications were confirmed by GC retention time of authentic standards.

Results and discussion Aroma characteristics of dried mandarin orange - blended green tea Twenty-one compounds 1

including 5 aldehydes, 5 alcohols, 6 terpenes, 4 ketones and 1 furan were identified in green tea. Forty-two compounds including 5 aldehydes, 9 alcohols, 23 terpenes, 2 furans and 2 esters were identified in mandarin orange. Fifty-two compounds including 9 aldehydes, 11 alcohols, 23 terpenes, 4 ketones, 2 furans and 2 esters were identified in mandarin orange - green tea. The main aroma components of green tea were linalool, nerolidol, β-ionone and hexanal. Linalool with floral odor was found in substantial amounts (32.70%). Nerolidol with flower note was found in large amounts (13.70%). β-Ionone with violet flower note was found in large amounts (11.84%). Hexanal with green note was found in considerable amounts (7.04%). The main aroma components of mandarin orange were limonene, (Z)-ocimene and γ-terpinene. Limonene with citrus and lemon note was found in substantial amounts (62.03%). It is used as for food, perfumery, cosmetic and pharmaceutical industries. (Z)-Ocimene with citrus and flower note was also found in large amounts (19.35%). Phenyl acetaldehyde (6.81%) with lilac and hyacinth flower aroma, and γ-terpinene (4.92%) with woody note were also found in considerable amounts. The main aroma components of mandarin orange - green tea were limonene (72.18%), (Z)-ocimene (8.29%), phenyl acetaldehyde (6.15%), γ-terpinene (5.14%) and linalool (1.00%). (Z)-Ocimene and γ-terpinene were originated from the mandarin orange, and limonene and phenyl acetaldehyde also were originated mainly from the mandarin orange, but a small amount of these were originated from the green tea. Linalool was originated from the green tea, but a small amount of it also were originated from the mandarin orange. The aroma of green tea blended with dried mandarin orange is characterized by having a high percentage of terpenic compounds such as limonene, (Z)-ocimene and γ-terpinene, which were detected as citrus odorant group. Therefore, mandarin orange - green tea turned unflavored tea into special tea with a good and preferred flavor. Aroma characteristics of dried citron - blended green tea Forty-four compounds including 4 aldehydes, 12 alcohols, 26 terpenes, 1 ketone and 1 furan were identified in citron. Fifty-three compounds including 9 aldehydes, 13 alcohols, 26 terpenes, 2 ketones 1 furan and 2 esters were identified in citron - green tea. The main aroma components of citron were limonene (68.52%), γ-terpinene (9.75%), (Z)-ocimene (7.55%) and (E)-ocimene(6.90%). (Z)-Ocimene was found in large amounts, an isomer of (E)-ocimene was also identified. (E)-Ocimene has a sweet and herb odor. The main aroma components of citron - green tea were limonene (71.74%), γ-terpinene (9.76%), (Z)-ocimene (5.38%), (E)-ocimene (4.36%) and linalool (1.00%). γ-Terpinene and (E)-ocimene were originated from the citron, and limonene and α-terpinene also were originated mainly from the citron, but a small amount of these were originated from the green tea. Linalool was originated from the green tea, but a small amount of it also were originated from the citron. The aroma of green tea blended with dried citron characterized by having a high percentage of terpenic compounds such as limonene, γ-terpinene, (Z)-ocimene and (E)-ocimene, which were detected as citrus odorant group. Therefore, citron-green tea also turned unflavored tea into special tea with a good and aromatic flavor.

Acknowledgements This work was supported by Blue-Bio Industry RIC at Dongeui University as a RIC program under Ministry of Knowledge Economy and Busan city.

References Choi, S. H., Shin, M. K. and Lee, Y. J. (2003) Volatile aroma components of green tea scented with lotus (Nelumbo nucifera Gaertner) flower. Food Sci. Biotechnol. 5:540-543 Lee, D. S., Woo, Z. W. and Kim, N. S. (2004) Comparative analyses of the flavors from hallabong (Citrus sphaerocarpa) with lemon, orange and grapefruit by SPTE and HS-SPME combined with GC-MS. Bull. Korean Chem. Soc. 25:271-279

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