Overnight tea refers to any tea that is left brewing for more than 12 hours.
Some people make tea in the evening and leave it overnight, or make tea in the morning and continue to drink it in the evening.
Should we drink this tea? Read on and find out.
Room temperature tea
Tea is usually brewed in hot water which releases tea tannins, caffeine, amino acids and other substances that we enjoy in small doses.
If the tea leaves are left to soak they will continue to release these compounds, which can make the tea bitter and unpleasant to drink. It may even cause heart palpitations and damage the gastrointestinal mucosa.
In addition, if the tea soup is left at room temperature for too long, the amino acids in it will interact with the bacteria and microorganisms in the air and begin to spoil. If you continue to drink it, it can cause gastrointestinal discomfort.
What about cold brew tea?
The tea leaves of cold brewed tea are placed in cold water or ice water at the beginning, rather than brewed with hot water. The cold water releases far fewer tannins than in hot water. So cold brewed tea can be stored in the refrigerator overnight or even longer. The taste will not become bitter and unpleasant as long as it is stored at a low temperature.
However, even if cold brewed tea is properly refrigerated, it should be consumed within 3 days. Otherwise, the taste of the tea may become stale due to oxidation.
How about putting hot tea in the fridge?
Since cold brewed tea can be kept for a longer time, does putting hot tea in the refrigerator have the same effect? Generally not recommended.
In the first step of brewing with hot water, the tea tannins and flavor compounds will be released in large amounts. After being refrigerated and cooled down, the tea flavor will be lost.
If the hot tea needs to be put into the refrigerator, be sure to take out the tea leaves, and drink the tea as soon as it has cooled. The taste and quality of hot-brewed tea both deteriorate quickly, so the tea should be consumed within an hour or two after it has cooled.
Of the two brewing methods mentioned above, it can be seen that cold-brewed tea needs to be brewed in cold water over a long period of time, and hot-brewed tea needs to be brewed in hot water and consumed as soon as possible. The two methods are not interchangeable.
Does overnight tea cause cancer?
There are many discussions on the Internet talking about the dangers of drinking overnight tea, particularly as it is related to cancer. The idea is that overnight tea will harm your health and cause cancer because the tea contains amines that are converted into nitrosamines, a well-known carcinogen.
It must be clarified that amines are ubiquitous in food, but only free amines react with nitrite to form nitrosamines. Furthermore, the pH value of most tea leaves is about 5 (weak acid). According to research, when the pH value is around 3.5, nitrosamines are most likely to be produced. Therefore, even though overnight tea may have a theoretical link to carcinogenic nitrosamines, the amount of nitrosamines produced in tea is negligible compared with other foods that have high levels of amines. There is no concern that drinking overnight tea may cause cancer.
Compared with low risk of carcinogenicity, a much bigger concern is the microbial contamination caused by improper preservation of tea, especially sugary and milky teas. Once the tea appears cloudy and thick, it should be discarded immediately regardless of whether it has been brewing overnight or only for a few hours.
The containers for brewing hot tea can be made of glass, ceramic, 304 or 316 stainless steel, and titanium.
Plastic products are not suitable for hot tea, but BPA-free water bottles are generally accepted as food-safe and can be used for cold brew tea.
Iron and aluminum products are definitely not suitable and must be avoided.
Use a neutral detergent to clean the container and gently rinse. Do not use a steel brush, which can scratch the material and allow bacteria to breed inside the container.
The first infusion is not for drinking
The first short brew of tea allows the tea leaves to expand while removing any dirt and dust that may remain on the tea leaves.
Do not drink while it's hot
A water temperature of 85-95°C is ideal for bringing out the best flavor of oolong tea, but it is not a suitable temperature for drinking. The best temperature for drinking tea is about 60°C.
Habitual drinking of hot water or tea above 70°C has been associated with an increase in esophageal cancer. Hot beverages can also scald the esophagus mucosa, causing oral mucositis, esophagitis and other related diseases, which may lead to cancer over time.
After the tea has been served, you can let it stand, enjoy the tea fragrance, then drink it only after it has cooled down.
Don't leave hot tea for too long
Consume the tea as soon as possible after brewing.
If the hot tea is left for too long the taste degrades and the tannins in tea can irritate the stomach. In addition, it can also be a breeding ground for bacteria which can cause intestinal problems.