In Taiwan it’s all the rage, and it’s catching on elsewhere too: making tea by steeping leaves in cold water. Test-tube studies done at the Italian Universita Politecnica delle Marche show that if you do this with white tea or Oolong tea it’s even healthier.
You can make tea by pouring freshly boiled water on tea leaves, but you can also soak the leaves for two hours in cold water. This way you get more aroma, less bitter taste and, what’s more, the tea contains less caffeine. This way of making tea is becoming more popular. But is it healthier, the Italians wanted to know.
Well, it depends on the kind of tea you use. White tea is healthier if it is brewed cold; for other tea it makes no difference. The figure below shows the amount of polyphenols that the researchers found in hot and cold-brewed tea.
The researchers tested the antioxidant effect of the tea by bringing LDL cholesterol, copper and tea into contact with each other. In the body, unhealthy LDL cholesterol only becomes dangerous if it is oxidized. The Italians imitated this by using copper in their test-tube experiment. Antioxidants can delay this reaction. The longer the delay, the more powerful the antioxidant.
The figure below shows that cold-brewed white tea, Oolong and black tea protect the LDL cholesterol better than hot-brewed tea. For green tea it makes no difference how you brew it.
If you test the antioxidant effect of the tea in a different way, you get a graph like the one below. Here it is only the antioxidant effect of white tea that is increased by cold brewing.
White tea contains the polyphenol ECG, which is one of the more powerful antioxidants found in tea. The researchers suggest that this polyphenol is released more easily into the solution by steeping white tea in cold water rather than brewing the tea in boiling water.
Hot vs. cold water steeping of different teas: Do they affect antioxidant activity?
Abstract
A new popular way of making tea, especially in Taiwan, is to steep leaves in cold water. Here we investigate whether antioxidant activity of teas may be affected by hot or cold water steeping and if this correlates with their polyphenol content and metal-chelating activity. A set of five loose tea samples, consisting of unblended and blended teas, was analysed following their infusion in either hot water (90 °C, 7 min) or cold water (room temperature, 2 h). Antioxidant activity, measured as hydrogen-donating ability, using the ABTS· and DMPD assays, showed no significant differences among hot or cold teas, except in the case of white tea, where significantly higher values were obtained after cold water steeping, a recurrent finding in this study. The antioxidant activity of the teas correlates well with their total phenolic content and metal-chelating activity. Cold teas were, however, generally better inhibitors of in vitro LDL conjugated diene formation and of loss in tryptophan fluorescence. The results of this study contribute to gaining further knowledge on how the potential health benefits of this popular beverage may be maximised by the different methods of preparation.
Source: http://www.sciencedirect.com/science/article/pii/S0308814609011091
