Tea leaves that have been stored for a period, whether vacuum-packed or not, will undergo some changes. The chlorophyll and oxidative products of polyphenols in the tea leaves will cause them to age, turning yellow or red. If the leaves were inadequately withered or dried initially, the tea soup may become bitter and astringent. Furthermore, if stored improperly, they might even develop mold. Therefore, when you reopen tea that hasn't been consumed for a while, there are some issues to pay attention to before drinking.

First, confirm whether the tea leaves have moldered. You can place the leaves in your hand and inspect them under a light or give them a light sniff. If there is a moldy smell, they should not be consumed and can be used as plant fertilizer.

If the dry leaves have a grassy smell or other off-odors, you can ask a professional tea roaster or tea shop to handle them. If there is only a slight stale or aged taste, you can use specific brewing methods to address it.

Method One: Use water at a higher temperature, ideally boiling. The first infusion should be longer than usual, then discard the liquid. Starting from the second infusion, reduce the brewing time by half compared to usual. Brew quickly and try to drink it while hot.

Method Two: Lower the water temperature by a few degrees and brew for the normal duration. This can help avoid bitterness and astringency in the tea soup.

Method Three: It's better to switch to brewing in a large pot. You can use a higher water-to-leaf ratio ("pot mother"), which will improve the taste.

If you have tea at home that has been stored for a long time, confirm if it is moldy. If it has developed some off-flavors, try these three brewing methods; they might help restore a taste closer to its original state.