What cold is doing, and what it is not
Cold storage slows chemical change, and every process that degrades a fragile tea slows with it: the departure of volatile aromatics, the slow non-enzymatic oxidation that dulls the leaf, the lipid oxidation that produces the stale note. That is the whole of the benefit and it is a large one. What cold does not do is stop the leaf being a hygroscopic material. A frozen tea is still exchanging water with the air in its container, still able to take up moisture if the air around it is damper than it is, and still able to give it up. The freezing point of the small quantity of water held in dry leaf is not a threshold the tea crosses cleanly, and the practical implication is that a freezer is a very cold storage room rather than a suspension. Sprint 31 gives the domestic method that follows from this and it stands: divide at the outset into portions small enough to be used within a few weeks, seal each as well as the household can manage, freeze the lot, and remove one portion at a time, warming it fully while still sealed before opening. What this page adds is that the appliance the portions go into is not one thing.
The defrost cycle, and why frost-free is the wrong appliance
A frost-free freezer keeps its interior clear of ice by warming the evaporator periodically and draining the melt away. The consequence for anything stored inside is twofold: the cabinet temperature rises slightly on each cycle before falling again, and water is continuously being removed from the air in the cabinet. Both are deliberate, both are the reason the appliance is convenient, and both are the opposite of what a store wants. The temperature cycling is a repeated small version of the swing that stability is meant to eliminate. The drying is why unwrapped food in such a freezer develops the desiccated surface commonly called freezer burn. Tea in a genuinely sealed barrier is largely protected from both, which is the important qualification — but the seal is now doing more work than it would in a static freezer, and a zip bag or a folded pouch is not a barrier at this standard. A chest freezer or an older static model, which forms ice and is defrosted manually, holds a much steadier temperature and does not run the drying cycle. Where a household has both, the static one is the better store, and where it has only a frost-free model the answer is to seal harder rather than to abandon the method.
Sealing for a freezer specifically
The requirement is a barrier against water vapour, not merely against liquid. A laminate pouch with an aluminium layer, heat-sealed or very tightly folded and clipped, is a good barrier; a zip closure is a modest one; a plastic food bag is weak; and a rigid container with a plain snap lid is usually the worst of the group despite looking the most secure. The arrangement that works in most kitchens is the tea inside its original laminate pouch, that pouch closed as tightly as possible, and the whole thing inside a second sealed container or bag so that a failure of the first is not a failure of the store. Vacuum sealing is genuinely useful for this one case, with the caveat Sprint 31 records: a full draw crushes fluffy and twisted leaf, so sealing the tea inside its own pouch first, or using a pulse setting, avoids paying for the barrier with the shape of the leaf. Label every portion with the tea and the date in something that survives cold and damp, because frozen packets are unusually easy to lose track of and an unidentified portion two years later has defeated the whole exercise.
Odour in a freezer, which is not the problem people expect
A freezer is drier and much less aromatically active than a refrigerator, which is why it is the better of the two for tea, and it is not inert. Aromatic transfer is slower at low temperature but it does not stop, and a freezer that contains fish, fruit, prepared food and ice cream is a shared atmosphere like any other. The saving grace is that the barrier required for moisture is also a barrier for aroma, so a tea sealed properly for the reasons above is protected for this reason too, and a tea sealed badly is exposed on both counts at once. There is a second and less obvious hazard, which is the ice itself. Frost accumulating on the outside of a package in a static freezer will melt when the package comes out, and a laminate pouch pulled from a freezer and left on a worktop develops a film of condensed water on its exterior — which is harmless if the seal holds and is exactly how a marginal seal gets wet. The habit worth forming is to bring a portion out into a dry room, leave it entirely alone until it is at room temperature, wipe the outside, and only then open it.
How long a frozen portion is actually good for
Longer than the same tea at room temperature by a substantial factor, and not indefinitely. The processes that dull a tea are slowed rather than halted, so a frozen green tea drifts slowly rather than not at all, and the honest expectation is that a well-sealed portion carries a spring tea comfortably through to the following spring and is doing less well by the year after. That horizon happens to match the useful case exactly: the method exists so that a seasonal tea with an annual supply can be drunk until the next harvest, not so that a cupboard can be stocked for a decade. Where a household finds itself with three-year-old frozen portions, the tea is not ruined and it is no longer the product that was bought, and the correct conclusion is a purchasing one. There is one further limit worth naming. Each portion should experience one cycle, not several. A portion opened, resealed and returned to the freezer has been through a condensation event and a temperature swing and is now a worse store than the same tea would have been in a tin, which is why the portioning decision has to be made when the tea arrives rather than when it starts to fade.
What should never go in
Anything being aged, for the reasons the green-and-dark rule gives: cold arrests the process the tea was bought for, and the humidity and cycling of a domestic appliance are the wrong conditions besides. Matcha in a tin that is in daily use, because the condensation problem is worse for a powder — it clumps, takes water across its whole surface at once, and cannot be dried out again — and because the warming period a small tin needs is longer than any morning allows. Anything already opened and not resealed to a real barrier standard. Roasted oolong, which wants to be dry and settled rather than cold and cycled, and whose maintenance is a re-firing question rather than a temperature one. And any tea the household will actually finish within its good period anyway, which is most teas and is the honest answer for most people. Freezing is a specific tool for a specific problem — a genuinely seasonal tea bought in a quantity larger than a few months of drinking — and applying it more widely converts a sound technique into a source of condensation events. The purchasing decision remains the more powerful lever, and it is free.