No, storing green tea in a flask, especially a metal one, is generally not recommended for extended periods. While a flask might seem convenient for keeping tea warm, it can negatively impact the tea's flavor and quality.
Why Storing Green Tea in a Flask is Problematic
Several factors contribute to this:
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Oxidation: Green tea is highly susceptible to oxidation. Keeping it warm in a flask, even a well-sealed one, promotes oxidation. This process changes the tea's color to a brownish hue, similar to black tea, and makes the taste astringent and less palatable. [Reference: Simple tips to enjoy a nice cup of tea at office | HOJO Online]
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Flavor Alteration: Even if the flask is clean, it can impart its own aroma or absorb tea flavors over time, affecting subsequent brews. [Reference: Is it bad to drink green tea from a thermos flask? : r/tea]
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Material Interaction: Metal flasks, particularly stainless steel, can accelerate oxidation in green tea. Glass or ceramic containers are better alternatives for storing brewed green tea. [Reference: A friend recommended I start putting green tea bags in my (metal...]
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Difficult Cleaning: Thermoses can be difficult to clean thoroughly, potentially leading to mold or bacterial growth if not impeccably maintained.
Best Practices for Green Tea Storage
Instead of storing brewed green tea in a flask, consider these practices:
- Brew only what you need: Brew a fresh batch of green tea only when you plan to consume it.
- Use appropriate containers: For storing loose leaf green tea (before brewing), use airtight, opaque containers away from heat and light. [Reference: Green Tea Storage Tips – teavivre]
- If storing brewed tea briefly: If you must store brewed tea for a short time, use a well-sealed, non-metal container and consume it as soon as possible—preferably within a few hours. [Reference: Is it fine to drink green tea, which you made in the morning and ... ]
While some sources suggest that matcha can be stored in a thermos for a day [Reference: Storing matcha tea in a thermos? - Seasoned Advice], this does not apply to other forms of green tea. Matcha's unique preparation and properties may make it less vulnerable to some of the issues impacting other types of green tea.
