Cold brew tea techniques

Cold water extracts tea's compounds selectively. Amino acids (theanine, glutamic acid — the umami and sweet compounds) extract reasonably well at cold temperatures. Aromatic volatiles extract but slowly. Catechins (the astringent compounds) extract poorly at low temperatures. Caffeine extracts substantially less than at hot temperatures.

The net effect: cold-brewed tea is sweeter, smoother, less astringent, and lower in caffeine than the same tea hot-brewed. The aromatic character is present but more subtle — you trade some aromatic intensity for the smoother, sweeter profile.

This isn't universally better — hot brewing reveals aspects of the tea (especially aromatic complexity) that cold brewing doesn't. But for specific drinking contexts (afternoon and evening consumption when caffeine matters; summer cooling drinking; drinkers who find tannin character unpleasant), cold brew produces a meaningfully different and often preferable cup.

Cold brew technique is trivially simple:

1. Vessel: glass pitcher or bottle with a strainer or removable mesh basket. 1L+ is typical.

2. Leaf ratio: 1:30 to 1:60 leaf-to-water — more leaf per volume than Western brewing, less than gongfu. For a 1L pitcher, 15-30g of tea.

3. Water: cold filtered water poured directly over the leaves.

4. Time: 4-12 hours. Overnight in the refrigerator is the most convenient approach. 8 hours is a typical sweet spot; 12+ hours produces stronger cup.

5. Strain and serve: strain the leaves and serve cold over ice or chilled.

Most teas can be re-steeped at hot temperature after cold brewing — cold extraction is incomplete, and the leaves have substantial character remaining. Two for the price of one.

No specialized equipment is needed. A French press, a tea-infusing water bottle, a mason jar with a strainer, and a kyusu or gongfu pitcher all work.

Excellent cold-brew candidates:
- Japanese sencha (especially Shizuoka and Kagoshima): produces brilliant green cold cups, dramatically different from hot-brewed
- Premium gyokuro: cold-brewed in small portion of water produces concentrated sweet umami unlike anything in hot brewing
- Lighter Taiwanese oolongs (Alishan, Shanlinxi Qing Xin): cold brewing emphasizes the floral and creamy character
- White tea (Silver Needle, Bai Mu Dan): preserves the delicate honey character
- Lighter Chinese green teas (Long Jing): mellower than hot-brewed but pleasant

Acceptable cold-brew candidates:
- Lighter black teas (first-flush Darjeeling): works but loses much of the muscatel character
- Pu-erh (any style): works but most pu-erh deserves the depth that hot brewing provides

Poor cold-brew candidates:
- Wuyi yancha and other heavily-roasted oolongs: the roast character needs heat to extract
- Most darker/fully-oxidized teas: cold extraction is too incomplete
- Most flavored blends: flavors often don't cold-extract proportionally to the underlying tea

The pattern: teas with delicate amino acid character (sencha, gyokuro, lighter Taiwanese oolong) reward cold brewing most clearly; teas where the editorial character depends on roast or oxidation chemistry don't.

1. Using boiling water briefly, then cooling: this is iced tea, not cold brew. Different extraction; iced tea is hot-brewed strong then chilled. Cold brew uses cold water throughout.

2. Cold-brewing for too long: 24+ hours produces over-extracted bitter cup even at cold temperature. 4-12 hours is the window.

3. Using low-quality tea: cold extraction is unforgiving. The slow infusion reveals every defect. A mediocre tea that hot-brews acceptably may produce an unpleasant cold-brew.

4. Discarding leaves after one cold brew: most teas can be re-steeped hot for a different but rewarding second cup. Wasteful to discard after cold brew alone.

5. Cold-brewing for caffeine reduction without realizing it still has caffeine: cold brew has less caffeine than hot brew of the same tea, but it's not caffeine-free. Drinkers extremely sensitive to caffeine should still treat cold-brewed black tea or sencha as caffeinated.