Cold-brewing, cold-infusing, cold-steeping. Whatever name is applied, the process has often been perceived as secondary to the traditional use of hot water and tea leaves.
The science says otherwise. Cold-brewing may produce a better tasting and a more beneficial beverage than regular hot-water brewing. But what are the benefits? What kinds of teas produce these benefits, and how should cold-brewing be done?
Catechins and Polyphenols
This study indicates that, compared to hot water steeping, cold-brewing tea can result in tea liquor that has equal or greater levels of catechins (e.g. like EGCG) and polyphenols. Shiv Saria, owner of Darjeeling plantations, found polyphenol content was quite high in his cold-brewed Darjeeling:
@jasonowalker Had the concentrate tested at Darjeeling Tea Research & Dev Centre-extraction of polyphenols was more than in normal brew
— shivksaria (@shivksaria) July 26, 2013
But health claims and tea should not all be too hotly received.
In addition to some raised catechin levels, caffeine levels dropped. This study showed that caffeine in some cold-steeped teas was 50% to 66% lower than that of hot teas. Another study also noted the reduced caffeine and catechin boost in cold-infused tea.
How to Cold-Brew, & What Kinds of Tea Cold-Brew
Looking at a couple of studies together gives some clue as to how to best cold-infuse. This study claimed that white tea released more antioxidants (as related to polyphenol content) than other teas, but the teas were steeped with room temperature water for 2 hours. The studies above cold-brewed teas (green and other) for up to 12 hours at 4º C (about 39º F) and found noticeable beneficial components in their cold-brewed teas. Length of time does appear to make a difference. Err on the side of longer time instead of shorter. Also, temperature was a factor in caffeine release, so cold water steeping may be preferred to using room temperature water.
Cold brewing may not replace hot steeping year-round, but you have plenty of reasons to consider it when beating the heat, or for advance-steeping.
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