Comparison of chemical and biological characteristics of green tea, oolong tea and pu-er tea

Yap, Phooi Yee (2010) Comparison of chemical and biological characteristics of green tea, oolong tea and pu-er tea. Universiti Malaysia Sabah. (Unpublished)


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Tea (Camellia sinensis) is one of the most popular beverages consumed by over two third of the world's population. Tea is processed differently in different parts of the world to give green tea, pu-er tea or oo-long tea. In this study eight commercial tea samples of C. sinensis were extracted with 70% methanol. The samples were green tea A (T27), green tea B (T28), sui xian (T29), wang pi (T30), raw pu-er 2003 (T31), raw pu-er 2006 (T32), mature pu-re 2005 (T33) and mature pu-er 2007 (T34). T34 yielded the highest percentage of crude extract (28.15%). The methanolic tea extracts had total polyphenols content within 343.66 mg GAE/g - 497.33 mg GAE/g as analyzedu sing Folic-Ciocalteum ethod. Among them, T31 had the highest polyphenols content (497.33 mg GAE/g). The methanolic tea extracts were employedf or qualitative analysesu sing RP-HPLCa nd were found to have the major phenolic compounds such as catechins( EGCGE, CG),gallic acid and caffeine in the tea extracts. In addition, the methanolic tea extracts exhibited flavanoids content varied from 9.00 mg QE/g - 16.40 mg QE/gas analyzed using aluminium chloride (AICI3)colorimetric method.T32 had the highest flavanoids content (16.40 mg QE/g). In DPPH assay, the tea extracts had strongly scavenged activity of DPPH free radicals (varied from 47.76% - 90.26% compared to 32.77% by BHT, a synthetic antioxidant at 0.10 mg/mL). The antimicrobial activity of methanolic tea extracts were evaluated with Bacillus cereus, Escherichia coli, Listeria monocytogenes,Y ersinae nterocolitica, Vbno parahaemolyt cus, Enterobacter sakazaki, Salmonella enteritidis, Salmonella typh/mutfum,a nd Staphylococcusa ureus by using disc diffusion method. All the tea samples were found active against four bacteria which were Bacillus cereus, Usteria monacytogenes, Vibno parahaemolyticus, and Staphylococcus aureus. Present study shows that only T27, T28, T30 and T31 had potential inhibitory activity against MKK1 in signal transduction pathway and among them only T27 showed positive inhibition to MSG5. It is concluded that green tea and oolong tea do not show a very distinct difference between them. However, pu-er tea, shows distinct difference between raw pu-er tea and mature pu-er tea. Overall, raw pu-er has better results in all the phytochemical and biological tests that had run compare to mature pu-er. Besides, data in this study shows that phenolic and alkaloid extract of tea displayed good antioxidant activity. Therefore, tea extracts could be a promising source of natural preservatives in foodstuff.

Item Type: Academic Exercise
Uncontrolled Keywords: tea, green tea, pu-er tea, oo-long tea, methanol, extraction, antioxidant, phenolic, alkaloid extract
Subjects: T Technology > TP Chemical technology
Divisions: SCHOOL > School of Science and Technology
Depositing User: Unnamed user with email
Date Deposited: 30 Jun 2016 01:53
Last Modified: 30 Oct 2017 02:04

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