Will tea (loose-leaf tea or tea bags) stay fresh better (longer) if refrigerated?
The answer to this question was interesting to me as it defies a certain type of intuition, but makes intuitive sense once you hear it. People generally do not refrigerate loose-leaf tea. Why? For one, it is not necessary. But refrigerating loose leaf tea, or tea bags, can actually cause it to spoil. Why?
Relative humidity and condensation:
It does not always happen (depending on temperatures and humidities), but the risk of condensation when refrigerating a container of loose-leaf tea is very high. If any water condenses in the container of tea, even a small amount, it will ruin the tea in a very short period of time. Tea keeps for a very long period of time when dry. Once leaves become wet, they spoil very quickly. Even a small amount of cold water will cause the tea to infuse into the water, changing its chemical composition and flavor...and then if the tea leaves sit, they will eventually grow mold and spoil. Even in the low temperatures of a refrigerator, this process will happen much more quickly (a matter of hours and days) than the long time-scales over which loose-leaf tea will stay fresh if stored in a warm, even hot, but dry location.
Condensation frequently happens when you move airtight containers into a refrigerator, because the amount of moisture that air is able to hold changes hugely based on the air's temperature. A typical refrigerator keeps the temperature around 35-38F (1.67-3.33C), whereas typical room temperature is around 72F (22C). Room temperature air holds around three times as much water before becoming saturated. Thus, if you have a container that is over 33% humidity, and refrigerate it in a typical fridge, condensation will probably form. If the humidity is around 50% or higher, or if the initial temperature is higher and the humidity similar, it is virtually certain that there will be condensation. And given that many fridges cool unevenly, sometimes even approaching freezing in some areas (at freezing the amount of water air holds is about 1/4th as much as at room temperature), the chance of condensation in some part of the container is even higher--keep in mind, only some small part of the container needs to form condensation, and the tea will then quickly spoil.
Why risk it? Refrigerating tea is not necessary!
I have added this material to RateTea's page on storing tea as well, which contains a bunch of other tips and resources on how to properly store various types of tea, including discussion of how long tea stays fresh, and how aged teas are best treated differently from most other loose-leaf teas.