I believe that everyone has a friend who is very particular about drinking tea.
There is an elderly elder in our family who is very principled about drinking tea. For example, firmly believe that "overnight tea" can not be drunk; tea should be boiled in boiling water, not a second late; drink tea with a purple sand pot is the healthiest...
I also wondered why the tea brewed at seven or eight o'clock in the morning could be drunk at night, but the tea I brewed at seven or eight o'clock the night before could not be drunk the next morning. The same is about ten hours, is there any ingredient in the tea that is only a demon in the night? If it is best to brew tea hot water, what is the value of the now popular "cold brew tea"?
Today, we will briefly talk about the "health doorway" in drinking tea.
1, overnight tea in the end can not drink
What we call "overnight tea" is tea that has been stored for more than 10 hours every night.
Many people say that the main reason why overnight tea is harmful is that "there is nitrite (a carcinogen) for a long time".
However, there have been experimental tests (Beijing Nutrition Source Research Institute) [1]: in the Longjing, Pu'er and chrysanthemum teas that everyone often drinks, whether it is freshly brewed tea, or tea placed for 12 hours and 24 hours, the nitrite content is less than 0.2mg/L, far lower than the national sanitary standard for drinking water, which stipulates that the nitrite content in drinking water should not be higher than 1mg/L [2], so this statement is not established.
Again, some people are worried that the "glossy film" on the surface of the tea is not harmful, in fact, this layer of film and tea scale components are similar, mainly tea polyphenols, a small amount of metal elements (calcium, potassium, magnesium, etc.), we do not have to worry. The more "hard" the water, the more dirt there is, the more obvious this "membrane" is, and it is much better for friends who care about making tea with pure water.
But the brewing time is too long, you will find that the color of the tea becomes darker, the fragrance becomes lighter, the tasting value is reduced (because the tea polyphenols and other substances in the tea are oxidized), and one more, the tea is put for a long time, it may also be contaminated by microorganisms in the surrounding environment, think of the boiled water you open all night are afraid of dust or something falling into it...
Therefore, overnight tea is definitely not harmful, but it is better to pour out a re-brewed cup of fresh.
2, hot water tea or cold water to make tea
There is no gold standard for this, depending on the personal sensory experience.
For example, the important flavor substances in black tea, theaflavin, thearubicin, umami amino acids, astringent tea polyphenols, bitter caffeine together constitute the flavor of black tea, the higher the temperature, the stronger the flavor, the best brewing water temperature at 80 ~ 90 ° C, this temperature under the tea is the most refreshing, but not bitter or too thin.
Caffeine in tea can improve the body's state of excitement, which is what everyone calls "awakening", this brewing water temperature has been able to leach enough caffeine, but if the temperature is higher, too much caffeine leaching will make people tired, difficult to sleep, but also stimulate the gastric mucosa [3].
And it should be noted that long-term drinking of "hot tea" with too high a temperature (above 65 ° C) will also cause damage to the esophagus and increase the risk of esophageal cancer.
The "cold brew tea" that is now emerging is a new tea brewing method that is directly brewed with cold water to allow the aroma components and soluble substances of the tea to be slowly dissolved.
Compared with hot water, cold brew tea tastes sweeter, because when brewed at low temperature, there are fewer tannic acids and caffeine in the tea, and the amino acids with umami characteristics are dissolved first, so the tea taste is more fresh, there is no bitter taste, and the drawbacks such as tea discoloration and taste passivation caused by oxidation during hot water brewing are avoided [4][5].
In addition, studies have found that for green tea, long-term cold brews have higher antioxidant activity than hot brews, for black tea it is short-term hot brews, and white teas are less affected by temperature (brewing time is more affected) [6]. However, the tea itself actually has a high "antioxidant activity", do not pay too much attention to the difference in "antioxidant activity" caused by cold bubbles and hot bubbles.
3. Is it best to make tea with a purple sand pot?
Tea lovers love to use purple sand pots to make tea, mainly because it has a relatively high porosity, good breathability, and does not lose the original taste of tea.
But friends who love to drink tea also love to raise "tea scale", if not cleaned in time, over time this tea scale is infiltrated in the ventilation hole in the pot, easy to breed mold, drink every sip of tea there is mold as a companion.
So, make tea in a purple clay pot, and don't forget to keep the inside of the pot clean!
Ceramics and glassware are also good choices for making tea. As for other metal utensils, it is not recommended, and for long-term storage of food such as sauce and vinegar tea, metal utensils are not recommended!
bibliography
[1] Overnight tea is as venomous as a snake? CCTV experiment is still innocent[J].China Tea,2014,36(06):23.
Ministry of Health of the People's Republic of China, Standardization Administration of the People's Republic of China. GB 5749-2006 Sanitary Standard for Drinking Water[S], 2006.
Lu Li,Li Yuan. Analysis on the Effect of Different Brewing Temperatures on The Leaching of Chemical Components of Small Black Tea[J].Journal of Wuyi University,2016,35(09):8-11.
Yin Peng. Research Progress of Cold Brew Tea[J].Hunan Agricultural Sciences,2017(01):115-118.
[5] Liu Hong, Zhang Ming, Jiang Minghong, Qi Runyue." The Effect of Cold Brewing Tea brewing Method on the Sensory Quality of Black Tea, Green Tea and Oolong Tea[J].Beverage Industry,2016,19(06):38-41.
[6] Hajiaghaalipour F , Sanusi J , Kanthimathi M S . Temperature and Time of Steeping Affect the Antioxidant Properties of White, Green, and Black Tea Infusions[J]. Journal of Food Science, 2016, 81(1):H246-H254.
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