Have you ever made a cup of wonderful tea, had a sip and then forgotten about the cup until later?  When you come back and try it at room temperature, it tastes completely different than it did hot.  It seems counter-intuitive, being the same chemical compound on a technical level to register as such a different taste, but the effect is there nonetheless.

There are several reasons that temperature has such a profound effect on taste.  First, tea that sits out reacts with the air, oxidizing in the same way an apple browns after a few minutes.  This oxidization effects the flavor, usually in an undesirable way.  From personal experience, tea that sits out for a long time seems to lose some of the nuance of textural elements, becoming more flat.  Occasionally, and especially in the case of green teas and sheng pu’er, tea that sits out has a tendency to develop slight bitterness.

The main elements of temperature’s relationship to flavor that we are interested in can sometimes have a positive effect on taste.  In another article, we examine the effect of texture on the tasting experience.  It turns out that physical sensation synergizes with flavor to give us taste and trigger memory recall that influences our perception of tea.  Temperature is another element of physical sensation that needs to be explored to better understand what it does to our tasting experience.

One noticeable side-effect of room temperature or cold tea is the lack of smell.  Without vapors of tea being inhaled, we actually miss out on the “pre-taste” of the tea that primes the back of our throat and tongue to receive the tea itself.  Without smell, we start out with a more neutral palate.  This takes an element of smell / texture / taste synergy out of play, but also introduces new sensations.  By dulling the smell of the tea, the texture and taste are able to act without being influenced.  If a very sweet creamy Tieguanyin smells extremely floral for example, serving it cold removes much of the floral smell, and diminishes some of the floral flavor that we pick up.  However, it allows the sweetness to unfold on its own, likely edging towards the more vegetal side of flavor.  Cold-steeped Tieguanyin gives us a new perspective on the tea.  Coming back to the same tea hot, we can drink with more experience and consideration under our belt.

Besides limiting and isolating the effects of smell on taste, cold or room temperature tea changes the physical act of tasting.  With hot tea, we sip, aerating the liquor as it crosses our palate, which helps emphasize the lighter and more sparkling textures that the tea might have.  We do this instinctually not as a mechanism to improve taste but as a defense from scalding our tongue.  With the danger removed, we are free to drink the tea without aerating it or sipping it.  The interaction the tea has with the tongue is going to be heavier, favoring the stronger taste profiles of the tea over the lighter textures.  Sweetness is going to be emphasized, while bright and sparkling notes are diminished.  An interesting side-effect is that since cold tea can be consumed in greater volume, the aftertastes can often be even more intense than sipping small quantities.

One more mysterious phenomenon is that when drinking a tea hot or cold, interesting flavors come through, drinking a lukewarm tea usually has little to no taste.  Perhaps tea that is between room temperature and body temperature simply doesn’t capture our attention.  It seems that temperature on either end of hot and cold is telling our brain, “pay attention to this!” while room temperature simply doesn’t assert itself, making it harder to appreciate the flavors of the tea.  As an analogy, if somebody is talking, and you just can’t seem to pay attention, if they make a loud noise or clear their throat pointedly, your brain stops wandering and you snap back to listening.  Perhaps the hot and cold of tea is part of the magic, the loud noise that gets you to pay attention to the flavor that is coming.

As an extension of this thought, if hot tea is better than lukewarm for experiencing subtlety, than wouldn’t frozen tea be better than cold tea?  If you freeze a tea and then blend it into a slushie or shaved ice, you can only taste a small amount at a time, just like sipping on hot tea.  You have to put the frozen drink in your mouth and let it melt on your tongue.  The time it takes to melt and the extreme nature of the temperature emphasize with greater power the flavor and texture of the brew.

While hot tea may provide the most comprehensive experience (taste / texture / smell) it is only part of the full story.  Trying a tea iced, or even frozen informs your tasting vocabulary and reveals new elements of a tea that you might not otherwise have noticed.  As an added bonus, drinking something cold in the summer time can be very refreshing and more conducive to immediate comfort than hot tea.  The only downside is the Chinese line of thought that considers cold drinks a bit of a shock to the system.  If you find yourself sensitive to cold, then trying only small amounts of iced or frozen tea as a thought experiment may be best.  Otherwise, it makes for a great way to continue the exploration of what tea has to offer no matter the weather.

Cold Brewing Tips:

If you make an iced tea, it is always best to steep with cold water for several hours instead of brewing a concentrated tea with boiling water and adding ice.  Cooling hot tea can often lead to a weak and bitter brew, because either you have to steep for too long to get the right strength, or you end up adding so much ice that it melts and dilutes the tea.  Cold Brewing solves this conundrum and leads to the best and most potent iced teas possible.
-In general, use about 1tsp of tea per cup of water.
-Use filtered water or spring water
-Find a vessel that can ideally be covered.  Glass and metal have less flavor than plastic, and are therefore preferable, though new BPA-free culinary plastics are a good alternative.
-Fill the vessel with water that is just cool to the touch, add the tea leaves, stir and refrigerate.
-Allow to steep for at least 5 hours, or overnight.  There is no need to remove the tea leaves, as they tend to sink to the bottom, and because the water is cold, don’t oversteep to bitterness.

To make frozen tea:
-Start with cold-brewed tea and fill an ice cube tray (preferably one with a cover to lock out freezer smells)
-Freeze the tea solid, and blend until a smoothie consistency is created.
-You need either a relatively powerful blender or a commercial juicer to achieve smoothie consistency.  If this is not possible, breaking up the ice and eating pieces of it is a good alternative.