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Brewing a cup of tea can be a great way to help you relax after a stressful day. But sometimes you may forget about your tea. What happens if you fall asleep and leave your tea out? Can you drink overnight tea?
To answer this question, I did some research. As you would expect, the answer depends on how you made your cup of tea and the conditions the tea was exposed to.
SHORT ANSWER – Drinking Day-Old Tea
Generally, you should avoid drinking tea that has been left out overnight. This can allow bacteria and mold to grow, which can cause serious health problems. The tea will also start to lose all its flavor. However, some forms of tea will always be older than a day and are safe to drink nonetheless.
So, it’s probably best to avoid drinking tea that has been left for too long. But what makes this so dangerous, and how can you tell whether it’s still safe to drink? Let’s take a deeper look at this issue.
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1. Your Tea Will Oxidize
If you leave out your tea for longer than a few hours, you will taste a difference in taste. The tea will lose some of the floral and vegetal notes, but also the bitterness that may be present.
This is for the same reason that black tea tends to be less bitter than green tea. The oxygen in the air can oxidize some of the chemicals present in the tea.
This happens faster with brewed tea or wet tea leaves than with the dry tea leaves in storage. To avoid oxidation an loss of flavor when storing tea, I recommend using air-tight tea containers like these (link to amazon) to store your tea.
Change In Color
You can easily notice the oxidation of your tea by looking at the color. Tea changes color from lighter to darker color. You may have noticed this effect with green or white tea already.
Starting with a pale yellow or green color, the liquid will become browner and browner and finally turn to a very dark red-brown just as a strong black tea would look like.
Change In Taste
The oxidation will not only change the color but will also change the taste of your tea. Just as more oxidized tea (black tea) will taste different from less oxidized tea (green tea), you will taste the difference between fresh and day-old tea you drink.
The floral and vegetal notes prominent with young green tea will fade a few hours after brewing the tea. Bitterness and complex flavors will also decrease noticeably with day-old tea. This is partially why cold-brewed teas can taste sweeter than regular tea.
Drinking overnight tea that has been oxidized is completely safe! The problem with left-out tea is that of microbial activity and not the oxidation or age itself.
2. Drinking Yesterdays Tea Can Be Dangerous
Growth Of Microorganisms
With the age of your tea, there will not only be oxidization going on. It is also possible that the tea could be containing bacteria and mold. The teacup can provide a great environment for microorganisms like these to grow.
Both bacteria and mold can seriously impact your health if you drink overnight tea that has gone bad. Both bacteria and mold need only be present in tiny amounts to allow for rapid growth. The brewing methods influence how long it takes for the microorganisms to ruin your tea.
Bacteria can grow quite quickly in a warm and moist environment. If your tea leaves smell acidic or taste off, there is a good chance this is due to large numbers of bacteria being active and reproducing.
Mold takes a bit longer than bacteria to grow to a dangerous amount. Under ideal conditions, which are wet and warm environments, mold will take 24 to 48 hours to grow visibly. You will be able to see, smell and taste the growth of mold. If you notice any off-taste, throw away your tea!
The microorganisms present shortly after brewing the tea are largely influenced by the water temperature used to make it. If you use lukewarm water or cold-brew your tea, you will not kill off any bacteria or mold present in the tea.
By using boiling water to rinse your tea or brew your tea directly, you kill and remove much of what can destroy your tea. If you have used boiling water, there is a higher chance for you to be able to drink your day-old tea.
3. Reheating Yesterday’s Tea To Drink
If you want to drink yesterday’s tea, you might want to reheat your tea. In some cases, you might be able to get around the potential health problems by doing this, as you kill off the bacteria and mold before consuming.
You should not drink any tea that has direct signs of bacteria or mold! But to be safe with any tea that hasn’t been brewed recently, the heating will help. Heat the tea to at least 190 °F (88 °C) to kill all microorganisms.
Whether or not it is a good idea to reheat and drink the tea depends on how long the tea has been left out. If it has been just a few hours, there is no reason not to drink the tea. If it has been much longer than 12 hours, it is not a good idea.
Reheating has an impact on the taste of your tea, though. Your tea will most likely become bitter and less complex. The reheating will remove some of the volatile compounds responsible for taste.
4. Is Ice Tea And Sun Tea Safe To Drink?
A type of tea that is almost always left steeping for half a day or more is cold-brew. Both ice tea and sun tea are forms of cold-brewing tea. Ice tea is mostly brewed for over a day in the refrigerator while sun tea is brewed for a few hours in direct sunlight.
The perfect way to cold-brew tea is by using a bottle with integrated filter. My personal favorite is the Hario Cold-Brew Bottle, which is available on Amazon.
Neither of these teas ever reaches temperatures high enough to kill off microorganisms. Are these teas still safe to drink? The cold temperature of a refrigerator slows the growth of bacteria and mold significantly. This form of cold brew is generally safe.
Sun tea can be dangerous to consume, depending on how long you leave it out. The tea will not go bad within a few hours, but if left overnight outside or at room temperature, the risk is much higher. Since the tea is never heated, I would not drink day-old sun tea.
Even ice tea does expire after two or three days. I recommend that you should leave it for no longer than three days. After this time the flavors can start to taste a little off. This indicates the growth of microorganisms in your tea. When this happens, it’s best to avoid drinking the tea and create a new batch.
5. There Are Some Uses For Overnight Tea
Let’s assume that you have forgotten about your tea and left it out overnight. The tea has developed an off-taste and you are not going to drink the tea. Wouldn’t it be a shame to waste the tea, especially if you have invested in high-quality tea? What could you do with the tea?
You can use the tea as natural fertilizer for your plants. As tea is made from plant material, many of the nutrients necessary for plant growth are present in your leftover tea. Even though you shouldn’t drink it, the plants will happily absorb the nutrients. Be sure to dilute the tea first, though. You do not want highly concentrated tea to harm your plants.
There’s a lot more to learn about tea! If you are looking for a good place to start, I highly recommend the book Tea: History, Terroirs, Varieties. You can check its current price on Amazon here.