When people began exporting tea in the 17th century, thin sheets of lead was used to line the inside of heavy wooden crates to protect the product through the long voyage from physical vigour, the sun, moisture and exposure to air. Though time has changed but the nature of tea has not. The basic understanding that tea is vulnerable to these elements is the basic concept in proper tea handling and storage.
Light changes tea much more dramatically than most people would understand. In farm markets we see farmers spreading out their harvests under the sun to attract buyers. In teashops we see tea displayed in glasses under spotlights. These are all very bad practices but they just have to do it to attract sales.
Light is a powerful reduction agent. It turns all the fragile good tasting elements of tea into either indissoluble matters or bad tasting compounds. Put a batch of tea out to expose it under light for one day and compare its infusion with another batch of the same tea properly stored and you’ll immediately experience what I mean.
Even if you expose it in an airtight container, the aroma and taste will all be dramatically altered. Think what you could have got if you buy it from that big glass display.
Air and Moisture
A properly processed tea has a moisture level between 3 to 6%. It is a powerful absorption agent. You can basically use it as a deodourizer or a dehumidifier in the fridge or shoe cabinet, if you do not mind its cost.
That is exactly why tea has to be kept in a very airtight container.
One thing that oxygen in the air does to the tea is to oxidize its many tasteful, aromatic and salutary ingredients. Here is an example: when a fine green tea such as Longjing is stored in a light-tight, but not air-tight container, it gradually turns reddish and tastes very poorly. Thearubigen and theabrownins are formed giving that reddish colour, out of oxidation of the tea’s original richly stored polyphenols.
The one grease that easily comes into contact with tea is the natural (or applied) grease in the human hand. Avoid contact as much as possible until before usage. Like photons in light and oxygen in the air, grease binds with the contents of tea to form undesirable materials.
When you see in a tea dealer that tea is being touched liberally and put back into the bulk, avoid buying from him. The greased tealeaves put back into the bulk is like a seed put into the soil. Oxidation triggered by this greased handful spreads to the rest of the bulk to turn it bad, though gradually.
Residual enzymes in the leaves and trace oxygen remains in the tea pack continue to change the chemical composition of the tealeaves, however gradual it is. Heat hastens these oxidation processes.
Therefore, contrary to popular practice, your kitchen cabinet is not a good place to store tea. The heat, humidity and possible seepage of grease from cooking into the tea container are all factors that shorten the tea’s shelf life.
Similarly, any place that is humid, hot, or exposed to intense light is not a good spot.
All fine green teas; light fermentation teas; and green style oolongs, such as Tieguanyins, store much better in the fridge between 5~8°C. The shelf life can be extended for at least one year (two when the tea is properly dried) when the tea is properly packed.
All teas stored cold need to be brought back to room temperature before the pack is open. Moisture in the air can condense on the leaves as soon as the pack is open, if when the leaves are cold.
Other teas can be shelved in room temperature a lot more flexibly, although as much below 25°C is preferred. Although your tea would have been securely packed in light tight containers, strong lights should still be avoided to slow down photo-reduction of the pack materials themselves. If stored in the fridge, please make sure extra insulation is in place to avoid fridge odour coming in contact with the leaves. Refer to the material section for properly packing your leaves.
Tea that requires further maturing, such as Puers and charcoal baked oolongs, should not be shelved under 10°C, when maturing slows down quite dramatically. Optimum temperature is between 20 to 25°C. When storing such teas in porous containers, the optimum relative humidity is between 60 to 70%. Some people argue to store tea at higher humidity to hasten aging. The resultant tea, though mellow enough, is rarely clean tasting. Sweetness is also sacrificed.
Maturing brown style oolongs does not require storing them in porous containers. Treat them as other tea and keep them sealed until your destined usage time. I shall discuss more about tea maturing in a later article.
In cooking, we chop an ingredient into smaller pieces so that its aroma or taste can come out easily to blend with the others. Basically we break up the cell walls and increase the surface areas for contact. However, we do not want our stored tea to come into contact with air and moisture more quickly by breaking up the leaves. Keep the leaves intact by avoiding excessive handling of the leaves, shaking the container or stacking up soft containers.
Most people having been in old style teashops must have seen tea put in large, loosely covered containers that open and close many times daily. Some teas are put out in display. As a result, most people tend to think that tea can be handled quite casually, may be like they would spaghetti or dried pepper. I am not a specialist in other food products so I cannot say if they are mistreated, but tea definitely is.
While there is not much to waste in low-grade products, letting the quality of a fine tea deteriorate is sinfully wasteful, and a disregard of all the hard work and craftsmanship that made every single fine leaf. It is like hanging a Da Vinci in the front porch, or a Ming scroll in the bathroom.
Though putting tea in a proper container is a simple matter, it takes persistence for people to change a bad habit. I hope as awareness spread, the consumer regains the common sense that was once basic in the 17th century.