Research Corner: Interesting Journal Articles

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pedant
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Mon Feb 26, 2018 2:30 pm

please share links to journal articles that you find interesting

if you have thoughts and reflections on the article you're sharing, feel free to post those as well :D
also, if it relates to a conversation happening elsewhere on the forum, i think it would be helpful to mention that context

ps: i may edit posts in this topic for formatting purposes
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pedant
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Mon Feb 26, 2018 2:36 pm

here's an article posted by tealifehk in a topic about teapot cleaning:

Analysis of lipophilic compounds of tea coated on the surface of clay teapots (2015)
Chung, Tse-Yu et al.
Journal of Food and Drug Analysis , Volume 23 , Issue 1 , 71 - 81

https://www.sciencedirect.com/science/a ... 9814000945
Abstract: 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
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pedant
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Mon Feb 26, 2018 2:48 pm

Effect 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
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
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Shine Magical
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Mon Feb 26, 2018 3:31 pm

pedant wrote:
Mon Feb 26, 2018 2:48 pm
Effect 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
...
What does this mean? "The statistical differences were not all significant among Zisha, Zhuni and stainless steel pots."
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pedant
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Mon Feb 26, 2018 6:02 pm

Shine Magical wrote:
Mon Feb 26, 2018 3:31 pm
What does this mean? "The statistical differences were not all significant among Zisha, Zhuni and stainless steel pots."
well, they quantitatively measured stuff in the tea made in different tests with different pots.
of course the numbers they got are not identical for different tests, but then they had to decide if those differences in measurements for pot A vs pot B are great enough to actually mean anything.

like if i try to do research to test a hypothesis that "tuesday is the warmest day of the week", and it turns out that on average, tuesdays are a fraction of a degree warmer according to my data... is that hypothesis really true? or is it just by chance that my data says that?

they try to decide by doing a statistical analysis (described in the paper) and then use a p-value cutoff of 0.05 (i.e. 5%).
the analysis spits out a p-value which is kind of a margin for error.
this basically means that for a result to be "significant" (statistical term), they have to be at least 95% "sure" that the difference was big enough to actually mean anything. 5% margin for error is a common cutoff they pick in research. it's arbitrary.

that sentence is just saying that not all of the results they got were considered statistically "significant". you have to read the paper for the specifics.
for example, they said they measured that zhuni teapot tea has less caffeine than glass teapot tea.
for them to say that result is significant, their statistical analysis of their caffeine measurements has to say that there's at least a 95% chance that the caffeine difference is from them using different kinds of teapots and not something else.

also, if and only if it is legal for you to do so where you reside, you can try to access this and other papers via "sci-hub" (google it).
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tealifehk
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Mon Feb 26, 2018 6:26 pm

Great article pedant! Thanks for sharing!
wildisthewind
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Fri Mar 09, 2018 6:48 pm

Anyone know of research that discusses the effects of different dissolved minerals on extraction from tea leaves? Trying to figure out what the ideal mineral composition would be for tea water, more specifically than just 20-150 ppm TDS.
Ethan Kurland
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Fri Mar 09, 2018 9:53 pm

Nice category & comments Pedant. This forum is exceptional for having some members who are not intellectually lazy. I am lazy 99% of the time. Nonetheless, I read a long study done by Tufts University a year or so ago on the effect or lack of effect on antioxidants.

3% of people are effected at all by antioxidants. The very slight effect antioxidants have on this small minority is not 100% positive. Antioxidants may help the healthy people of this 3% remain healthy; & help people who are ill suffer more from their illnesses. That is the conclusion.

Believe me, no one who has worked to get plenty of antioxidants paid me any mind nor read the study that I referred them to.

On this forum so advice has been repeated many times which is: thickness of teawares walls matters a lot (more than tiny differences in composition) as well as quality of tea, water, & preparation.

Nonetheless, we will read..... thanks
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pedant
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Sun Mar 11, 2018 1:15 am

from bobdole2000:

Quality Development and Main Chemical Components of Tieguanyin Oolong Teas Processed from Different Parts of Fresh Shoots
Yong-Quan Xu, Pan-Pan Liu, John Shi, Ying Gao, Qiu-Shuang Wang, Jun-Feng Yin
Food Chem. 2018 May 30;249:176-183. doi: 10.1016/j.foodchem.2018.01.019

https://www.sciencedirect.com/science/a ... 4618300190
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.
Image
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Victoria
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Tue Apr 17, 2018 8:18 pm

Quantitative validation of nicotine production in tea (Camellia sinensis L.). Published: April 9, 2018

Takashi Ikka, Hiroto Yamashita, Ikuya Kurita, Yasuno Tanaka, Fumiya Taniguchi, Akiko Ogino, Kazuya Takeda, Nobuhiro Horie, Hiroshi Hojo, Fumio Nanjo, Akio Morita.

http://journals.plos.org/plosone/articl ... ne.0195422
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).
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debunix
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Wed Apr 18, 2018 4:53 pm

Nicotine in tea? Surprised, here. They're quite remotely related to the Nicotiana genus, and both are Asterids.

But I guess if your leaves are as tasty as C sinensis, you have to protect yourself....
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Victoria
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Wed Apr 18, 2018 5:50 pm

debunix wrote:
Wed Apr 18, 2018 4:53 pm
Nicotine in tea? Surprised, here. They're quite remotely related to the Nicotiana genus, and both are Asterids.

But I guess if your leaves are as tasty as C sinensis, you have to protect yourself....
Yes, my thought also, since nicotine acts as a pest repelant protecting the leaves from being eaten.
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pedant
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Wed Apr 18, 2018 6:29 pm

they bring up the possibility of sample contamination, but their evidence is compelling.

https://doi.org/10.1371/journal.pone.0195422.s004
https://doi.org/10.1371/journal.pone.0195422.t005

they found that nicotine concentration in the roots was high compared to other organs (tobacco is like this too).

also, they aseptically grew tea seedlings. although the seeds themselves contained nicotine, all parts of the seedings tested had higher nicotine concentrations than the original seeds. this suggests that nicotine was not conserved and that the seedlings made more of it.

they also tested aseptically cultured Yabukita cells from a cell line that's been cultured weekly since 1994.
the growth medium was nicotine free, but the cultured cells contained nicotine. i'm sold

edit:
the obvious question: can you feel that nicotine?
it looks like 10g dry leaf contains less than 7μg.
you probably need hundreds of μg to feel anything, so no.
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Victoria
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Wed Apr 18, 2018 10:05 pm

pedant wrote:
Wed Apr 18, 2018 6:29 pm
edit:
the obvious question: can you feel that nicotine?
it looks like 10g dry leaf contains less than 7μg.
you probably need hundreds of μg to feel anything, so no.
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.
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Wed Apr 25, 2018 9:36 pm

Earliest tea as evidence for one branch of the Silk Road across the Tibetan Plateau
Published: 07 January 2016

Houyuan Lu, Jianping Zhang, Yimin Yang, Xiaoyan Yang, Baiqing Xu, Wuzhan Yang, Tao Tong, Shubo Jin, Caiming Shen, Huiyun Rao, Xingguo Li, Hongliang Lu, Dorian Q. Fuller, Luo Wang, Can Wang, Deke Xu & Naiqin Wu

http://www.nature.com/articles/srep18955
https://www.ncbi.nlm.nih.gov/pmc/articl ... po=4.16667
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.
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