|Hot or not? That could be a matter of health or ah... well almost death ;-)|
How come? Well, in the study Vanessa de Carvalho Rodrigue, et al. conducted, it made a huge difference in terms of the total phenol and flavenoid content of the extracts (=the aformentioned teas) when the scientists used cold water instead of water that was 80°C "hot".
During the hot extraction procedure, a total of 2.0 g of the sample was extracted with 100 mL of water distilled at 80 °C. In contrast to how you would do it at home, though, the extraction process was propelled by stirring the glass for 450s (7:30 min). A similar procedure was used for the cold extract. The only differences were that (a) the extraction was done with 20 ml cold water and only 0.5 g of tea and (b) took 120 minutes during which the infusion was kept still, at room temperature (20–25 °C), and was stirred manually every 30 min (Damiani et al., 2014).
All extracts were filtered, transferred to Falcon tubes and immediately frozen at −20 °C (dark) for later analysis in order to prevent oxidation by light and oxygen.
|Figure 1: Total phenol & flavenoid content tea after extraction with hot or cold water (de Carvalho Rodrigues. 2015).|
What matters more than phenol and flavenol numbers, though, are (a - primarily) the antioxidant activity of the their sum (see Figure 2) and (b - secondarily) the presence of specific bioactive compounds like theobromine, chlorogenic acid or even caffeine (see Table 1).
|Too much tea (way more than 2 cups) may mess w/ your thyroid | more|
|Figure 2: Total antioxidant activity of the hot and cold extracts from various teas according to DPPH+ and TROLOX assays; sign. effects were observed only in the TROLOX assay (de Carvalho Rodrigues. 2015).|
- de Carvalho Rodrigues, V., da Silva, M. V., dos Santos, A. R., Zielinski, A. A. F. and Haminiuk, C. W. I. (2015), Evaluation of hot and cold extraction of bioactive compounds in teas. International Journal of Food Science & Technology. doi: 10.1111/ijfs.12858