Determination of L-Theanine and Caffeine Contents in Tea Infusions with Different Fermentation Degrees and Brewing Conditions Using the Chromatographic Method
This study aimed to determine the caffeine and L-theanine contents in tea infusions prepared under varying fermentation degrees, brewing conditions (temperature and time), and serving methods (tea bag/loose-leaf). Infusions of six tea types (green, white, yellow, oolong, black, and Pu-erh) and vario...
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MDPI AG
2025-06-01
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| Series: | Foods |
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| author | Gamze Ayakdaş Duygu Ağagündüz |
| author_facet | Gamze Ayakdaş Duygu Ağagündüz |
| author_sort | Gamze Ayakdaş |
| collection | DOAJ |
| description | This study aimed to determine the caffeine and L-theanine contents in tea infusions prepared under varying fermentation degrees, brewing conditions (temperature and time), and serving methods (tea bag/loose-leaf). Infusions of six tea types (green, white, yellow, oolong, black, and Pu-erh) and various serving forms of green, white, and black tea were brewed at 80 °C and 100 °C for 2, 5, and 10 min. Contents were analyzed using reversed-phase high-performance liquid chromatography. Caffeine levels were highest in black and yellow tea (14 ± 1.0 mg/200 mL and 13.8 ± 0.2 mg/200 mL, respectively), both of which were significantly higher than the levels in green, white, and oolong tea (11 ± 2.1 mg/200 mL; 5.8 ± 0.7 mg/200 mL; and 4 ± 1.6 mg/200 mL, respectively; <i>p</i> < 0.001), whereas Pu-erh tea (13 ± 2.9 mg/200 mL) had caffeine levels comparable to that of black tea (<i>p</i> > 0.05). L-Theanine levels were highest in black and green tea (12.3 ± 2.8 mg/200 mL and 12.5 ± 2.5 mg/200 mL, respectively), and these levels were significantly higher than those in the other tea types (<i>p</i> < 0.001). Brewing temperature only affected caffeine levels n, whereas L-oolong tea (4.4 → 13.5 mg/200 mL, <i>p</i> < 0.05); theanine remained stable (<i>p</i> > 0.05). Longer brewing times significantly raised both components (e.g., yellow tea caffeine levels rose to 53 ± 16.9 mg/200 mL at 10 min; <i>p</i> < 0.05). In black tea, cup-sized bags yielded higher caffeine levels (39 ± 9.9 mg/200 mL) than loose-leaf (24 ± 7.2 mg/200 mL) and teapot bags (<i>p</i> < 0.001). Serving method had no effect on green and white teas (<i>p</i> > 0.05). In conclusion, fermentation rate, brewing conditions, and serving method were found to influence the caffeine and L-theanine levels of tea infusions. |
| format | Article |
| id | doaj-art-f838e6008e0a4c8c9b35e225b34b84a8 |
| institution | Kabale University |
| issn | 2304-8158 |
| language | English |
| publishDate | 2025-06-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Foods |
| spelling | doaj-art-f838e6008e0a4c8c9b35e225b34b84a82025-08-20T03:28:37ZengMDPI AGFoods2304-81582025-06-011413231310.3390/foods14132313Determination of L-Theanine and Caffeine Contents in Tea Infusions with Different Fermentation Degrees and Brewing Conditions Using the Chromatographic MethodGamze Ayakdaş0Duygu Ağagündüz1Department of Nutrition and Dietetics, Acıbadem University, Kerem Aydınlar Campus, Ataşehir, Istanbul 34755, TurkeyDepartment of Nutrition and Dietetics, Gazi University, Emek, Ankara 06490, TurkeyThis study aimed to determine the caffeine and L-theanine contents in tea infusions prepared under varying fermentation degrees, brewing conditions (temperature and time), and serving methods (tea bag/loose-leaf). Infusions of six tea types (green, white, yellow, oolong, black, and Pu-erh) and various serving forms of green, white, and black tea were brewed at 80 °C and 100 °C for 2, 5, and 10 min. Contents were analyzed using reversed-phase high-performance liquid chromatography. Caffeine levels were highest in black and yellow tea (14 ± 1.0 mg/200 mL and 13.8 ± 0.2 mg/200 mL, respectively), both of which were significantly higher than the levels in green, white, and oolong tea (11 ± 2.1 mg/200 mL; 5.8 ± 0.7 mg/200 mL; and 4 ± 1.6 mg/200 mL, respectively; <i>p</i> < 0.001), whereas Pu-erh tea (13 ± 2.9 mg/200 mL) had caffeine levels comparable to that of black tea (<i>p</i> > 0.05). L-Theanine levels were highest in black and green tea (12.3 ± 2.8 mg/200 mL and 12.5 ± 2.5 mg/200 mL, respectively), and these levels were significantly higher than those in the other tea types (<i>p</i> < 0.001). Brewing temperature only affected caffeine levels n, whereas L-oolong tea (4.4 → 13.5 mg/200 mL, <i>p</i> < 0.05); theanine remained stable (<i>p</i> > 0.05). Longer brewing times significantly raised both components (e.g., yellow tea caffeine levels rose to 53 ± 16.9 mg/200 mL at 10 min; <i>p</i> < 0.05). In black tea, cup-sized bags yielded higher caffeine levels (39 ± 9.9 mg/200 mL) than loose-leaf (24 ± 7.2 mg/200 mL) and teapot bags (<i>p</i> < 0.001). Serving method had no effect on green and white teas (<i>p</i> > 0.05). In conclusion, fermentation rate, brewing conditions, and serving method were found to influence the caffeine and L-theanine levels of tea infusions.https://www.mdpi.com/2304-8158/14/13/2313L-theaninecaffeineteabrewingHPLC |
| spellingShingle | Gamze Ayakdaş Duygu Ağagündüz Determination of L-Theanine and Caffeine Contents in Tea Infusions with Different Fermentation Degrees and Brewing Conditions Using the Chromatographic Method Foods L-theanine caffeine tea brewing HPLC |
| title | Determination of L-Theanine and Caffeine Contents in Tea Infusions with Different Fermentation Degrees and Brewing Conditions Using the Chromatographic Method |
| title_full | Determination of L-Theanine and Caffeine Contents in Tea Infusions with Different Fermentation Degrees and Brewing Conditions Using the Chromatographic Method |
| title_fullStr | Determination of L-Theanine and Caffeine Contents in Tea Infusions with Different Fermentation Degrees and Brewing Conditions Using the Chromatographic Method |
| title_full_unstemmed | Determination of L-Theanine and Caffeine Contents in Tea Infusions with Different Fermentation Degrees and Brewing Conditions Using the Chromatographic Method |
| title_short | Determination of L-Theanine and Caffeine Contents in Tea Infusions with Different Fermentation Degrees and Brewing Conditions Using the Chromatographic Method |
| title_sort | determination of l theanine and caffeine contents in tea infusions with different fermentation degrees and brewing conditions using the chromatographic method |
| topic | L-theanine caffeine tea brewing HPLC |
| url | https://www.mdpi.com/2304-8158/14/13/2313 |
| work_keys_str_mv | AT gamzeayakdas determinationofltheanineandcaffeinecontentsinteainfusionswithdifferentfermentationdegreesandbrewingconditionsusingthechromatographicmethod AT duyguagagunduz determinationofltheanineandcaffeinecontentsinteainfusionswithdifferentfermentationdegreesandbrewingconditionsusingthechromatographicmethod |