Proper storage of your loose leaf teas can greatly extend their shelf life. There are essentially just five simple rules that you need to follow: store in an airtight container, away from moisture, odour, heat and light. That’s it. However, if you want to get a bit more nerdy about the how and why, please read on.
Although teas are often labelled with an expiration date, this is done primarily to satisfy food safety requirements. In reality, tea is a very shelf-stable product, that is likely to go stale before spoiling. In general, spoilage only occurs in teas that have accumulated too much moisture. In recent years, pu’er teas from the 1920-30s have been sold at auction for astronomical prices. Of course, exclusivity is a big factor, but also an indication that, contrary to expiring, some teas do in fact get better with age… but only if stored properly.
An easy rule of thumb is that teas which have been less oxidised during the production process, will have a shorter shelf life. Or even more simply put, those that look more green, will expire faster. Although the enzymes responsible for oxidation are denatured during the kill-green stage of production, inevitably some oxidation will continue to occur, albeit very slowly, thereafter. As such, green teas will continue their progression to full oxidation, thus slowly becoming ‘black’ teas.
In order to enjoy teas at their fullest flavour and the way that was intended by the producer, we can use the following guidelines. The timer starts from when the producer finished the product.
● within 12 months for green, yellow and white teas
● within 18 months for green oolongs
● within 24 months for black oolongs and black teas
● indefinite for aged white tea, aged oolongs and fermented teas (e.g. pu'er)
(Note: vacuum sealed and/or frozen teas may be kept for longer than the above suggestions)
Next, we the outline the five rules of storage, in no particular order of importance.
Contact with air will allow enzymatic oxidation to happen. Therefore, green, yellow and white teas will be more vulnerable to quality alteration, and eventually deterioration, in case of non-airtight storage. Oolongs and black teas have a higher degree of oxidation and will be affected slower by exposure to air. The easiest steps to take are: vacuum pack when storing for a long period of time; or, keep in an airtight container when putting away for frequent use. When vacuum packing, additional measures available to eliminate oxygen are nitrogen flushing or inserting oxygen absorbers. Nitrogen flushing is sometimes offered by the production facility or distributor. Oxygen absorbers are easy to purchase and are simply small packets containing iron and salt. The iron will bind with, and eliminate, the oxygen to form rust. When using airtight containers, if possible, remember to always squeeze out as much air as possible before resealing. If hard containers are used, it is advisable to scale down container size to best fit the amount of tea being stored. In other words, empty space inside the container needs to be minimised in order to avoid unnecessary exposure to oxygen. Another tip would be to divide a bulk purchase into smaller quantities, in order to avoid reopening the one large parcel repeatedly, thus allowing air in.
Where not to store: in an airtight container which is too big for the quantity of tea being stored
Dried tea leaves are hygroscopic, which means they absorb moisture, including humidity from the air. Moisture can create the right environment for various chemical processes, such as fermentation, as well as lead to mould growth. Also, we basically do not want not want our tea coming into contact with moisture any sooner than when we intend to brew it, otherwise valuable flavour compounds will be released and just wasted.
Where not to store: in damp spaces, such as underneath the sink or basement
Tea absorbs adjacent odours. This can be both good and bad. An example of when this can be used to good effect is when producing flower scented teas. Dried tea leaves are interspersed with fresh flower petals, such as jasmine and osmanthus, and allowed to rest overnight during which the tea leaves absorb the flower aromas. At all other times, and to keep things easy, just keep your teas away from all other odours. This, for example, also applies to keeping your oolongs away from your chai or coffee.
Where not to store: in the spice cabinet, pantry, next to the oven or stove
As we should remember from chemistry class, chemical reactions happen faster at higher temperatures. In the case of tea, this also means faster oxidation and fermentation, among other things. These are exactly the things we are looking to control and slow. You might be thinking that the fridge is a good idea? Unfortunately, it is not that simple. Only vacuum sealed teas can be kept in the fridge or freezer. The main reason is that if not vacuum sealed, upon taking the tea out of the cold and into room temperature, condensation will begin to form on the cold surface of the leaf and immediately be absorbed by the leaf. When taking a vacuum sealed package out the fridge or freezer, wait for it to reach room temperature before opening.
Where not to store: under direct sunlight, next to the oven, stove or heat-emitting appliances
Exposure to light will discolour the leaves and therefore also the brew. Green leaves will turn yellowish, whereas black leaves will be bleached. This is part of a process known as photodegradation, which sets off a chain of chemical reactions, and may result in a metallic taste in your tea.
Where not to store: in any transparent plastic or glass
The rules of storage are different for aged teas. Aged oolongs are generally kept in airtight containers in order to slow oxidation. In addition, some of these aged oolongs are taken out of their containers every few years and re-roasted in order to remove excess moisture that has accumulated. This extends shelf life, as well as adds complexity to their flavour profile by imparting smokey and malt notes. On the other hand, fermented teas, such as pu’er, are generally not kept in airtight containers. Rather, they are kept in special storage rooms with a controlled environment, where some interchange with air and moisture is encouraged. As we can imagine, the science of aging tea is rather a form of art that takes many years and patience to truly master.
Just follow the above five steps and your teas will stay fresh the longest, likely even past their shown expiration date. However, the one true test should be your own senses. If the tea smells or tastes off, get rid of it and brew yourself another one.
With this information in hand, you should have all the basics to attempt successfully storing away some of your loose leaf teas. A crowd favourite for storage is Bao Zhong, as the green character of this oolong tends to gracefully transition into a more oxidised profile showing more rounded dried fruit, nutty and woody notes.
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