- Humidity/moisture: Despite the fact that tea is a relatively "dry" substance, it does have an ideal moisture content, which is usually 2%-3%. Allow the tea to come into contact with water before you intend to use it, and it's as good as gone. Over longer-term storage, humidity in the air can raise your tea's moisture level by several percentage points within a few months, resulting in the oxidization of the elements responsible for tea's flavor and quality.
- Air: Probably the most obvious of the five, oxygen also contributes greatly to long-term oxidization of tea. Just like any food item, if exposed to air for long periods of time, tea will lose flavor and begin to taste stale.
- Light: Exposure to UV rays can cause chemical changes in your tea, reducing its vitamin and nutrient content and changing the color from vibrant green to dull brown. Exposure to direct sunlight is the worst.
- Heat: High temperature can speed up the chemical processes that age tea.
- Odor: Certain types of tea are especially good at absorbing other smells; if you store your tea near strong-smelling food or other odors, its character will likely be diminish and be obscured by the odor it has acquired.
Aside from these general guidelines, different containers have strengths and weaknesses when it comes to tea storage. When we sell bulk tea to customers at Miro Tea, we use resealable polyfoil laminate bags like this one:
These bags are generally very excellent storage options: when heat-sealed, they're airtight (especially if they've had the air squeezed out when packaged), and since they're opaque, they block light exposure. The downsides are that they aren't attractive, aren't easy to organize in a cupboard, and don't offer much protection from heat. I've had very good results storing fresh-harvested green tea in unopened polyfoil bags for up to a year inside a cooler in a cool basement--when I finally opened the bags, the tea tasted nearly as fresh as it did back in April of the year before.
Once you open a polyfoil bag, it's probably a good idea to find a better storage option. Although many of the bags are resealable, a zip-loc seal is never completely airtight. Depending on how long you intend to store the tea before drinking all of it, you have a number of options. For short-term storage here at Miro Tea, we use these glass Bodum containers:
They're nice because they show off the beautiful tea leaves and the rubber seal helps keep out air and moisture. I'd only recommend this kind of storage if you're going though your tea quickly, though, since the temperature and light blockage are nil.
The ideal container is undoubtedly this one, a ceramic jar with locking, sealing lid:
We use these for medium-term storage at Miro, and they're ideal because of their airtight seal and thick walls, which block light and temperature fluctuation. I've personally had the best results with this kind of container, especially versus tins and canisters, which never seem to keep tea fresh for long. Just remember--no matter what container you use, try to match the size of the container with the amount of tea leaves. If there's a lot of empty space in the container, that means your tea is coming into contact with more flavor-stealing air and humidity!