ORANGE, Calif.
Chapman University recently teamed up with specialty tea manufacturer QTrade Teas & Herbs to examine the nutritional content of cold-brewed teas.
The results could revolutionize the way we think about loose leaf tea.
The goal of the study was to examine the nutritional content of black tea when brewed at different temperatures. Graduate students from Chapman University’s Food Science Program tested the teas for their phenolic and fluoride contents at a range of temperatures from hot, to room temperature, to cold. The black tea was used for all of the tests (BOP Fannings from Argentina) but half of the samples were brewed loose, while the rest were brewed in nylon mesh pyramid-sachet bags.
As expected, higher phenolic content was always found in teas that were steeped at higher temperatures. Tea that was brewed in boiling water had more than five times the phenolic content of the other samples, in spite of the fact that the other teas were steeped for a longer period of time.
As for nutritional content, these researchers overwhelmingly vouched for hot-brewing teas rather than cold brewing.
“This was consistent with our hypothesis,” study-leader Jonathan Tong said while presenting the research, “we were fairly confident that higher temperatures would yield a better extraction and a higher phenolic rate.”
A related finding though, was less expected.
Across the board, all of the teas that were steeped in pyramid sachet bags yielded notably higher phenolic levels than those that were steeped loose. The students’ review of previously published studies shows that these results are consistent with previous research as well. One theory for the counterintuitive result is that pyramid-sachet bags force tea leaves to remain completely submerged throughout the steeping process. By contrast, some tea leaves steeped loose will float to the surface of the water. With more surface area exposed to the air as opposed to the water, a poorer extraction results and the phenolic content is lower.
While this could have potentially wide-reaching implications for the industry, the researchers caution that more study is necessary before any industry-wide claims can be made about the healthiness of pyramid sachet brewing versus loose leaf.
The students noted that loose leaf tea, when brewed in a fully submerged “infuser ball” would likely extract phenolic content at levels equal to or above those found in the pyramid sachet bags.
Researchers report a dearth of scientific information regarding the fluoride content of tea. Their research found that there is enough fluoride in this variety of black tea to satisfy half of the USDA’s recommended daily dose of fluoride in just one cup of tea.
The researchers quickly concede that further research is needed before hard conclusions are drawn. They recommend that further research be conducted on teas from multiple origins and oxidation levels, as well as examining the affect of agitating the water on extraction levels.
Though they found that cold-brewing teas results in less robust phenolic content, other factors may be interesting to study in the future, such as the aromatic qualities of cold-brewing versus hot. The students are currently planning follow-up studies with the possibility of submitting their research to scientific journals next year.
Hot vs. cold water steeping of different teas: Do they affect antioxidant activity?
Author(s): Venditti, E (Venditti, Elisabetta)1; Bacchetti, T (Bacchetti, Tiziana)1; Tiano, L (Tiano, Luca)1; Carloni, P (Carloni, Patricia)2; Greci, L (Greci, Lucedio)2; Damiani, E (Damiani, Elisabetta)1
Source: FOOD CHEMISTRY Volume: 119 Issue: 4 Pages: 1597-1604 DOI: 10.1016/j.foodchem.2009.09.049 Published: APR 15 2010
Source: Chapman University