ABSTRACT


Study on Variation of Physicochemical Composition by Semi-fermentation using Fresh Leaves of Damyang Jukro-tea

Jeon Dong-Bok
Advisor : Prof. Kim, Kyong-Su, Ph.D
Department of International Tea Culture
Graduate School of Chosun University

This study was performed on the impact evaluation of growing environment and efficacy on three international varieties of Jukro-tea namely Korea, China and Japan by literature. The published work explain that there is no change in the cultivation among the three countries mention, which is the same as can be seen today as for Damyang Jukro-tea since period of the three Kingdoms.
Fresh leaves of Jukro-tea growth period were otherwise it is to making Damyang jukro-tea of high quality that after semi-fermentation and examined the variation of the composition and volatile organic compounds. A total of 136 volatile organic compounds were detected in the three types of sample fresh leaves of Damyang Jukro-tea. These were 91 compounds, amounting 98.53 mg/kg for 40 day leaves, 106 compounds (86.52 mg/kg) and 98 compounds (41.24 mg/kg) for 60 day leaves and 90 day leaves respectively, and was decreased as a longer growth period. The volatile organic compounds identified were a total of 159 species of from semi-fermented leaves of Jukro-tea. These were in 40 day leaves (103.9 mg/kg), 60 day leaves (259.56 mg/kg), and 90 day leaves (273.14 mg/kg). The overall content of the compounds to be increased as the longer growth period. The major volatile organic compounds C6 aldehyde, hexanal, (E)-2-hexenal content of fresh leaves was the highest for 90 day leaves but that of 40 and 60 day leaves were the same.
Hexanal and (E)-2-hexenal content was very low in semi-fermented 40 day leaves, while for 60 days leaves it was very high, but the 90 days leaves content was slightly changed. (Z)-3-Hexenol and (E)-2-Hexenol content were decreased in all semi-fermented leaves. Aldehyde compounds were the most abundant content in semi-fermented 60 day leaves and decreased slightly in semi-fermented 90 day leaves. Hexanal, (E)-2-hexenal, 3-methyl-butanal, 2-methylbutanal were the most abundant contents of semi-fermented 60 day leaves, which decreased in 90 day leaves and small amount were also detected in 40 day leaves. Furfural of sweet aroma was found in no difference according to the growth period.
Terpenoid compounds including geraniol, linalool, (E)-nerolidol, α-terpineol were found in the decreasing order of : 40 day ＞ 60 day ＞ 90 day. The four species compounds of linalool oxide were high in 60 day leaves. From fresh leaves to semi-fermented leaves, the content of geraniol was increased for 60 day leaves while decreased for 40 day leaves and 90 day leaves. Also from fresh leaves to semi-fermented leaves the content of linalool decreased for 40 day leaves while area% was decreased but 60 day leaves and 90 day leaves were unchanged. (E)-nerolidol content was increased much, regardless to the growth period of fresh leaves have been semi-fermented. Methyl jasmonate was found only in semi-fermeted 40 day leaves. (Z)-3-hexenyl hexanoate and (E)-2-hexenyl hexanoate are the unique flavor of tea which was found in higher amount in 60 day leaves than 90 days. β-ionone was in greater content only in semi-fermented 60 day leaves. (E)-β-damascenone was found in small amount only in semi-fermented 60 day leaves. D-limonene and β-bisabolene were most prominent in semi-fermented 60 day leaves.
Major catechin composition of fresh leaves of Damyang Jukro-tea were : EGCg, ECg, EGC while in semi-fermented leaves these were : EGC, GCg, EGCg. The EGC was the highest 7.12% in semi-fermented 60 day leaves, EGCg content of semi-fermented 40 day leaves was 9.94%, 60 days 6.80%, 90 days 1.79%. Catechin content of fresh leaves when semi-fermented, decreased on the whole. The caffeine content in 40 day leaves was 0.91%, 60 day leaves 1.65% and 90 day leaves 0.43%. After fermentation, the caffeine content remained in the same trend as in fresh leaves, but the amount in semi-fermented 40 day and 90 day leaves increased to 1.32% and 0.88 % while in 60 day leaves decreased to 1.40%. Pyrroles and pyrazines which have savory flavor created by fermentation were detected in small amount only in semi-fermented 40 day leaves. The antioxidant activities which are dependent on catechins namely EC, ECg and EGCg, whose amount was found decreased, with the fermentation progresses.
In conclusion we studied the different growth levels and harvest periods of Damyang Jukro-tea while fresh leaves semi-fermented to analyze the variation in physicochemical composition. The useful of the non-volatile compounds, Catechins, theanine and caffeine were compared by growth period of tea and their impact on sensory and flavor. Fresh leaves of Damyang Jukro-tea on semi-fermentation was found to partially volatile organic compounds the decrease was very minute on 60 day leaves were the most effective tea, reduce the non volatile compounds.
Especially, the content of the characteristic volatile compounds of jukro-tea increased by semi-fermentation in 60 day leaves. Thus a 60 day leaves were supposed, to be the best leaves for making high quality Damyang Jukro-tea.