Why Thermos Cups Discolor Tea
There are various types of tea sets, but from a scientific perspective, metal tea sets, enamel tea sets, plastic tea sets, and thermos cups are generally not ideal for making tea. Metal tea sets containing high levels of gold, silver, lead, and copper can lead to increased absorption of these metal components by the human body due to wear and tear, posing potential health risks.
While enamel tea sets offer the advantages of being less prone to bursting and durability, their tea-making effect is suboptimal. Particularly when the enamel is broken and the iron sheet is exposed, it can negatively impact tea quality, causing the tea to lose its original flavor and turn yellow, with a cooked soup appearance.
Brewing tea in plastic cups can result in the dissolution of odorous or harmful substances when exposed to boiling water. This not only affects the taste of tea but is also detrimental to human health.
Due to the consistently high temperature maintained in thermos bottles and tea cups, aromatic substances volatilize rapidly, diminishing the intended aroma of the tea. Simultaneously, the elevated temperature can lead to excessive leaching of tea polyphenols, resulting in a thick and bitter tea soup. Brewing green tea in a thermos cup, in particular, may make the tea soup taste sultry, cause discoloration, and compromise the tea fragrance.
A phenomenon occurs where tannins and theophylline in tea leaves precipitate and oxidize over prolonged soaking, not exclusive to green tea but applicable to any tea leaves steeped in a thermos cup for an extended period. Therefore, for the sake of health and well-being, it is advisable to avoid using a thermos cup for making tea.