• The Korean Journal of Food & Health Convergence
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• v.5 no.3
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• pp.7-20
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• 2019

The use of caffeine as a psychoactive stimulant in tea has been observed to have serious negative effects in humans' systems such as respiratory, nervous, cardiovascular, renal and skeletal systems. This study was carried out to assess the levels of caffeine in 10 different tea brands available in local market in Dutse, Jigawa State, Nigeria. Quantitative analysis of caffeine was performed by a simple and fast UV-Vis spectrophotometric methods using different solvents for extraction. The caffeine content in all the tea samples analyzed in this study were below the maximum allowable limits set by the USFDA. Tea have been associated with adverse health effects and the claims made by manufacturers about the benefits of tea do not highlight risks associated with excessive consumption of a combination of the ingredients contained in tea. Long term effects of tea consumption of children and young people have not been adequately studied. Therefore, it is recommended that further research be carried out on the adverse effects of energy drinks on children. Research is also needed to be done on the effects of the combination of ingredients on health and excessive consumption of those ingredients to children and adolescents. People need to be educated and given proper awareness on the health risks associated with caffeine containing beverages.

• Journal of the Korean Society of Food Science and Nutrition
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• v.21 no.6
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• pp.595-600
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• 1992

This study was performed to investigate the effects of dietary protein levels(5% and 15% PEP), caffeine or green tea powder on body fat deposition in rats. Male weanling Wistar rats weighting the average of 90g were allotted into 6 experimental groups, each of which was fed two different levels of dietary protein with or without caffeine or green tea powder(5p+0.15% caffeine ; 5p+6.1% green tea powder ; 15p+0.15% caffeine ; 15p+6.1% green tea powder) during 8 weeks of the experimental period. Caffeine and green tea powder were supplemented at the levels of 0.15% and 6.1% of experimental diets. The rats fed 5% PEP diet which had received caffeine or green tea powder showed significantly(p<0.01) reduced gain in body weight. The food efficiency of which rats fed both 5% and 15% PEP diet supplemented with 6.1% green tea powder was significantly low(p<0.05, respectively) compared with the control group. Rats fed diets containing 0.15% caffeine and 6.1% green tea powder showed the significant reduction(p<0.01) of hite adipose tissue weight, triglycerides levels of liver and plasma. The addition of 0.15% caffeine or 6.1% green tea powder to 5% PEP diet resulted in significantly(p<0.01) higher levels of plasma total cholesterol, free cholesterol, cholesterol ester, but HDL-cholesterol levels were significantly(p<0.01, in 5% PEP group) high. The atherogenic index(Tchol-HDLchol/HDLchol) in rats fed 6.1% green tea powder diets decreased especially compared with the control group.

• Journal of Microbiology and Biotechnology
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• v.28 no.7
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• pp.1147-1155
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• 2018

The degradation efficiency and catabolism pathways of the different methylxanthines (MXs) in isolated caffeine-tolerant strain Pseudomonas putida CT25 were comprehensively studied. The results showed that the degradation efficiency of various MXs varied with the number and position of the methyl groups on the molecule (i.e., xanthine > 7-methylxanthine ${\approx}$ theobromine > caffeine > theophylline > 1-methylxanthine). Multiple MX catabolism pathways coexisted in strain CT25, and a different pathway would be triggered by various MXs. Demethylation dominated in the degradation of N-7-methylated MXs (such as 7-methylxanthine, theobromine, and caffeine), where C-8 oxidation was the major pathway in the catabolism of 1-methylxanthine, whereas demethylation and C-8 oxidation are likely both involved in the degradation of theophylline. Enzymes responsible for MX degradation were located inside the cell. Both cell culture and cell-free enzyme assays revealed that N-1 demethylation might be a rate-limiting step for the catabolism of the MXs. Surprisingly, accumulation of uric acid was observed in a cell-free reaction system, which might be attributed to the lack of activity of uricase, a cytochrome c-coupled membrane integral enzyme.

• Food Science and Biotechnology
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• v.18 no.5
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• pp.1212-1217
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• 2009

This study examined the influence of manufacturing processes and extraction conditions on the chemical compositions of green tea. Green tea samples grown in various areas (Korea, China, and Japan) and processed by 4 different methods (steaming, pan-firing, steaming and pan-firing, and heavy roasting after steaming and pan-firing) were collected for study. The chemical compositions of the green tea extracts and infusions were different according to their processing methods and extraction conditions, including catechins, caffeine, and free amino acids contents. In all samples analyzed, (-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC), and theanine were determined as the major catechins and free amino acid, respectively. Studies of samples grown in the same area (Jeju; Korea) showed that there were significant differences in the concentrations of catechins and caffeine in extract and infusion according to the processing methods. These results indicate that processing methods influenced the chemical compositions of the green tea extracts and infusions.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.4
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• pp.295-299
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• 2004

The prices of domestic green tea products are relatively expensive and price differences within products of the same levels of quality are various. Also, there is no basic criteria on evaluation of green tea quality. To group 43 commercial green tea products into several parts by the principal component and cluster analyses, this work was done by use of 8 chemical constituents which were analyzed by NIR system. The principal component and cluster analyses revealed 8 groups. The first group included 16 products that had lower free amino acid and theanine contents. The second group included 5 products having higher free amino acid and theanine contents, but lower ash contents. The third group included 13 products showing medium values of 8 constituents. The IV group included 4 products having higher contents of moisture, free amino acids, and theanine. The V group included 1 product showing higher moisture but lower catechins contents. The VI group included 2 products that had higher moisture and catechins contents, but lower free amino acid and theanine contents. The VII group had higher moisture and catechins contents. The VIII group had higher ash and vitamin C contents. The free amino acid contents which were the most important in flavor evaluation of green tea quality did highly positively correlate with the contents of total nitrogen $(0.956^{**}),\;theanine\;(0.981^{**}),\;and\;caffeine\;(0.793^{**})$, but negatively with the contents of ash $(-0.884^{**})$. The catechins used as for functional ingredients did correlate with contents of caffeine(+) and vitamin C(-), respectively.

• Journal of the Korean Society of Food Science and Nutrition
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• v.12 no.2
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• pp.99-104
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• 1983

Chemical changes of major tea constituents by tea manufacture were examined by the quantitative masurements of tannin, caffeine, free sugars and total amino acid. The sample used in this experiments was fresh green and black tea leaves, green tea prepared by classical panning process and black tea prepared by commercial process. The results obtained are as follows: Compared with fresh tea leaves, tannin was increased 2% in green tea and decreased 56.5% in black tea by tea manufacture. Caffeine was increased 25.9% in green tea and decreased 3.1% in black tea. Total free sugars were decreased 78.2% and 76.7% in green tea and black tea, respectively. Total amino acids were decreased 26.1% and 18.8% in green tea and black tea, respectively.

• Journal of the Korean Society of Food Science and Nutrition
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• v.46 no.5
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• pp.639-645
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• 2017

Differences in bioactive compounds and antioxidant activities of aronia leaf (AL) extracts according to manufacturing conditions such as different number of pan-roasting and different temperatures were investigated. Both total polyphenolic compounds and total flavonoids contents were the highest in six time-pan-roasted AL tea extract ($37.96{\pm}0.48mg$ catechin equivalent/g and $19.96{\pm}0.44mg$ quercetin equivalent/g, respectively) among four tea samples. Antioxidative activities were also the highest in six time-pan-roasted AL tea extract with $IC_{50}$ 0.43 mg/mL and $IC_{50}$ 0.27 mg/mL based on DPPH and ABTS radical scavenging activities, respectively. HPLC analysis revealed that AL tea infusion did not have caffeine regardless of manufacturing conditions, whereas green tea infusion had 3.8 mg/g caffeine. Results demonstrated that AL tea can be expected as caffeine free leaf tea containing antioxidant benefits. Moreover, specific pan-roasting conditions of AL tea would be very important for its functional and sensory attributes.

• Journal of agriculture & life science
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• v.46 no.2
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• pp.49-61
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• 2012

This study was carried out to investigate the chemical composition and the inorganic constituents of the green tea at the 3 picking periods (Ujeon, Sejag, Jungjag) in Hadong. The results as follows ; The contents of chlorophyll, tannin, vitamin-c and total catechin were increased as picking periods increased but the contents of total nitrogen, total free amino acids, theanine and caffeine were decreased on the reverse. The inorganic constituents Mg, Ca and Mn were increased as picking periods getting late but the Na, K, B contents were decreased on the reverse. The contents of the total nitrogen, chlorophyll, total free amino acid, theanine, caffeine and total catechin and Na, Mg, Ca, B and Se were insignificant differences between Ujeon and Sejag.

• Journal of the Korean Wood Science and Technology
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• v.39 no.4
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• pp.370-380
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• 2011

This study was carried out to investigate the properties of soils in the sampling green tea farms and the chemical constituents of the green tea leaves at the 3 harvest stages (Ujeon ${\rightarrow}$ Sejag ${\rightarrow}$ Jungjag). The results as follows; The properties of the soils were sandy loam, loam, well drained and fertile-rich in phosphoric acids in general. The contents of chlorophyll, tannin, vitamin-c and total catechin were increased as harvest periods getting late but the contents of total nitrogen, free amino acids, theanine, caffeine were decreased on the reverse. The inorganic constituents Mg, Ca and Mn were increased as harvest periods getting late but the Na, K, B contents were decreased on the reverse. The contents of the total nitrogen, chlorophyll, total free amino acid, theanine, caffeine and total catechin and Na, Mg, Ca, B and Se were insignificant differences between Ujeon and Sejag.

• Korean Journal of Food Science and Technology
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• v.36 no.4
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• pp.542-546
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• 2004

Changes in contents of catechins, caffeine, free amino acids, and minerals in green tea loaves according to harvest periods were compared. Total catechin content increased from 40.61 to 52.04 mg/g, while that of caffeine decreased from 17.56 to 14.61 mg/g according to harvest periods. Regardless of harvest periods, composition of catechins was epigallocatechin (EGC)>epigallocatechin gallate (EGCg)>epicatechin (EC)>gallocatechin (GC)>epicatechin gallate (ECg)>catechin (C)>gallocatechin gallate (GCg)>catechin gallate (Cg). Free amino acid content in green tea leaves was highest in young loaves, and gradually decreased according to harvest periods. Theanine content was markedly decreased with leaf aging, suggesting taste of green tea may be changed from mild to bitter with increasing harvest period. Analyses of mineral elements in green tea leaves showed that Fe, Mn, and Mg increased with leaf aging, while Cu showed opposite trend. Results reveal that content of some chemical compounds in Korean (Posong) green tea was highly dependent on harvest period.