Tea Knowledge & Friendship
access tip: if it is legal for you to do so where you reside, you can try to access papers for free via Sci-HubAbstract: The surface of a clay teapot tends to be coated with a waterproof film after constant use for tea preparation. The waterproof films of two kinds of teapots (zisha and zhuni) used for preparing oolong tea and old oolong tea were extracted and subjected to gas chromatography–mass spectrometry analysis. The results showed that comparable constituents were detected in these films; they were primarily fatty acids and linear hydrocarbons that were particularly rich in palmitic acid and stearic acid. To explore the source of these two abundant fatty acids, the fatty acid compositions of fresh tea leaves, granules, infusion, and vapor of infusion were analyzed by gas chromatography. Fresh tea leaves were rich in palmitic acid (C-16:0), unsaturated linolenic acid (C-18:3), linoleic acid (C-18:2), and oleic acid (C-18:1), which were presumably from the phospholipid membrane. During the process of manufacturing oolong tea, the three unsaturated fatty acids may be substantially degraded or oxidized to stearic acid (C-18:0), which was enriched with palmitic acid in the tea granules and in the infusion. The vapor of the tea infusion is primarily composed of palmitic acid and stearic acid. Thus, the coated films of teapots mostly originated from the lipophilic compounds of the tea infusions.
Keywords: clay teapot; oolong tea; palmitic acid; stearic acid; surface coating
Abstract:
BACKGROUND: The flavor and quality of tea are widely believed to be associated with the pot in which the tea is made. However, this claim is mostly by experiences and lacks solid support from scientific evidence. The current study investigated and compared the chemical compositions of oolong tea made with six different teapot materials, namely Zisha, Zhuni, stainless steel, ceramic, glass and plastic.
RESULTS: For each tea sample, polyphenols and caffeine were examined by HPLC-UV, volatile compounds by GC/MS, amino acids by LC/MS and minerals by ICP-MS. The results suggested that tea infusions from Zisha and Zhuni pots contain higher levels of EGC, EGCG and total catechins and less caffeine than those from ceramic, glass and plastic pots and tend to have the lowest total mineral contents, potassium and volatile compounds in tea soup. The statistical differences were not all significant among Zisha, Zhuni and stainless steel pots.
CONCLUSION: Based on the overall chemical composition of the tea infusion, Yixing clay pots (Zisha and Zhuni) produce tea infusions that are presumably less bitter and more fragrant and tend to contain more healthful compounds than tea infusions from other pots. The results could partially explain why Yixing clay pots are among the most popular teapots. The beneficial effects of long-term repeated use of these teapots warrants further study.
© 2017 Society of Chemical Industry
What does this mean? "The statistical differences were not all significant among Zisha, Zhuni and stainless steel pots."pedant wrote: ↑Mon Feb 26, 2018 2:48 pmEffect of teapot materials on the chemical composition of oolong tea infusions (2018)
Liao, Z.-H. et al
J. Sci. Food Agric, 98: 751–757. doi:10.1002/jsfa.8522
http://onlinelibrary.wiley.com/doi/10.1 ... 2/abstract
...
well, they quantitatively measured stuff in the tea made in different tests with different pots.Shine Magical wrote: ↑Mon Feb 26, 2018 3:31 pmWhat does this mean? "The statistical differences were not all significant among Zisha, Zhuni and stainless steel pots."
The Tieguanyin oolong tea is popular in China. However, the quality development and chemical change during processing were still unclear. This study aimed to investigate the chemical compositions and quality of Tieguanyin oolong teas processed from different leaves of fresh shoots. The results showed the fermentation degree of oolong teas decreased from the first leaves to the fourth-fifth leaves, and was associated with the changes in infusion color (b∗) and chroma, as well as the contents of total theaflavins, (E)-nerolidol and indole. After shaking and setting, the differences in the water contents and the activities of polyphenoloxidase, peroxidase, and β-glucosidase of the tea leaves, significantly influenced the oxidation of catechins. The hydrolysis of volatile compounds might influence the fermentation degrees of the oolong teas processed from different leaves of fresh shoots. The results generated from the present study can be used in guiding the production of oolong teas.
Highlights:
Oolong teas processed from second and third leaves had better quality.
Fermentation degrees of Oolong teas decreased from first leaf to fourth-fifth leaves.
Theaflavins were found to relate to the fermentation degrees of Oolong teas.
Water content, PPO, POD and β-glucosidase influenced the fermentation degrees.
Abstract:
Endogenous nicotine was confirmed to be present in tea plants (Camellia sinensis L.) by liquid chromatography-tandem mass spectrometry of tea samples from tea-producing regions in six Asian countries. All samples contained nicotine (0.011–0.694 μg g−1 dry weight). Nicotine contents remained constant during manufacturing of green, oolong and black teas, implying that nicotine is stable against heating, drying, enzymatic oxidation and mechanical damage during processing. Flower buds and seeds of cultivar Yabukita also contained nicotine (0.030–0.041 μg g−1 dry weight). A comparison of two cultivars revealed that higher nicotine contents were found in the black tea cultivar Benifuki. All plant parts of hydroponic Yabukita contained nicotine (0.003–0.013 μg g−1 dry weight). Tea cells cultured in B5 medium as well as roots and stems of tea seedlings contained nicotine levels similar to those of new leaves from field-grown plants. Although the levels of endogenous nicotine in tea plants are extremely low and sample contamination cannot be discounted, these levels exceed the maximum acceptable limit in Japan (0.01 μg g−1 dry weight).
Yes, my thought also, since nicotine acts as a pest repelant protecting the leaves from being eaten.
I just checked out of curiosity since nicotine is my tempter; On average 1 cigarette = .7gr dry leaf = 15.96mg ( 15960μg ) of nicotine. So yes I’m glad to know, what is found in tea is really very minimal.
Abstract
Phytoliths and biomolecular components extracted from ancient plant remains from Chang’an (Xi’an, the city where the Silk Road begins) and Ngari (Ali) in western Tibet, China, show that the tea was grown 2100 years ago to cater for the drinking habits of the Western Han Dynasty (207BCE-9CE), and then carried toward central Asia by ca.200CE, several hundred years earlier than previously recorded. The earliest physical evidence of tea from both the Chang’an and Ngari regions suggests that a branch of the Silk Road across the Tibetan Plateau, was established by the second to third century CE.
