At the heart of it are two types of storage, depending on your aim:
An example of the first type of storage might be for a fresh Japanese Sencha, where one wishes to preserves its key characteristics for as long as possible.
And example of the second is a puer tea, where the general goal for many people is to age the tea over several years to achieve a fairly significant change in it’s flavour.
The main factors that affect the flavour of tea in storage are:
Regardless of the goal,all types of tea storage should share these same traits:
Practically, most tea is stored in a bit of a grey area. Not much thought is given as to what type of environment the tea is resting in—the tea is simply kept in its original packaging and stored somewhere easily accessible. For most types of tea, this will result in a slow but steady change in the teas flavour, depending on the exact storage conditions. The main point, is that it is not intentionallycontrolled storage.
Controlling tea storage allows us to achieve the desired outcome for the tea with greater certainty.
Let’s go back to the first example. You have just received a very fresh green tea, processed only a week prior. The main quality you admire in this tea is its ‘freshness’, i.e the strength of flavour that is directly influenced by how long it has been since the tea was processed.
Your options are to either drink it as soon as possible, and enjoy the tea over the coming days or weeks, or risk the tea becoming stale when left for too long.
Well, given the right environment, you could put that tea into complete stasis. We simply need to minimise the factors that cause it to age: oxygen, temperature, light, humidity.
If you were to nitrogen-flush and then vacuum pack the tea in an opaque, foil-lined bag that minimises oxygen exchange with the exterior, and then refrigerate or deep freeze it, the tea would barely change whatsoever, almost no matter how long you stored it. This type of extreme storage will stop any process of flavour change or ageing right in it’s tracks. It might seem a bit extreme, but this is what Japanese farmers have recently begun doing with their fresh withered tea leaves, before they are steamed, meaning they can make small batches of ‘shincha’ or fresh tea throughout the year. Similar realisations are happening with roasted coffee: nitrogen flush, vacuum pack, and freeze, and the beans will be fresh as can be upon opening months or years later.
Not everyone has the ability to nitrogen flush or vacuum pack at home, but often you can buy tea this way, in small packets so that you can open only what you need.
Practically at home, if you had a tea you want to minimise changes in, the best practice would be to keep it as cool, dark, and sealed/oxygen free as possible. This might mean using a ziplock bag and bath of water to displace as much air as possible before sealing and putting in the fridge, or freezer, or cool dark cupboard. This will still slow down the ageing of the tea significantly, should your wish be to have ‘fresh’ qualities preserved for a later date.
Now to the second example, ageing tea. Ageing means we are purposefully, again,controlling the environment the tea is stored in to produce a significant change in flavour.
For example, the goal almost universally with raw puer tea is to age the tea to some degree, to promote a smoother, more complex tea that has unique 'aged' flavours. The tea slowly changes from pale yellow/green to a more orange, red, or brown colour. Due to it's kill-green or 'sha qing' being done at a lower temperature and for less time than green tea, puer tea has more enzymes within the leave that are not denatured, meaning the tea is 'alive' in a sense. Expose the tea to the right conditions, and the tea will slowly ripen via enzymatic and microbial action. More heat and humidity increases the rate of growth of yeasts, bacteria, and other fungus, and a higher temperature means the enzymes will react with oxygen more quickly compared to a cold environment.
Thus practically, many people choose to store puer tea in more or less humid and hot environments to produce varying rates of change. This is a complicated and little understood topic scientifically, and we will delve into it deeply in another part of this series. But again, the key point is that by purposefully introducing heat, humidity, and oxygen to a tea, we are intentionally promoting a change in its flavour, rather than trying to inhibit it as in the case of fresh green tea.
In the middle of these two extremes, you have a grey area, where much tea is losing flavour due to exposure to the elements, but not readily developing flavour either. The storage has not been controlled in either direction. Most end consumer stored tea worldwide would fall into this category. Often the tea is bought, and left in its original packaging in an easily accessible place such as a pantry or cupboard. The temperature, humidity and other factors are not considered to a large degree.
Not every tea is suitable for controlled ageing, but generally white teas, oolongs, black teas, and puers can all be purposefully aged to achieve what is hopefully positive outcome. Green tea, due to its processing does not really 'age' in a positive sense—there are not enough enzymes left active to promote meaningful oxidation that would lead to positive flavour change, and the tea instead simply stales.
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