Generally, the shelf life of Green Tea at room temperature is around one year. However, factors that mainly affect the quality of Tea include temperature, light, and humidity. If stored properly, green tea can maintain its quality for a long time. However, if stored improperly, leading to excess moisture, it may expire in as little as two months. Once opened, green tea should be transferred to an airtight container for storage.

How to Tell If Green Tea Has Gone Bad

1. Scent

Stale green tea will have off odors such as musty, sun-dried, or moldy smells. Take a deep sniff of the dry leaves or the aroma of the brewed tea; if there are noticeable off odors, it's best to find fresh tea.

2. Appearance of Dry Leaves

If the color of the tea leaves is dark yellow and not crisp, it has likely gone bad. If you can only crush the dry leaves into small pieces with your fingers and the twigs do not break easily, this indicates the tea has spoiled. Unspoiled green tea typically contains about 7% water content and can be ground into powder.

3. Infusion Evaluation

The infusion of stale green tea will be brownish and heavy, lacking clarity. It will taste flat with no astringency or freshness. The refreshing sensation characteristic of green tea will be absent.

This change in the infusion is due to the oxidation of the main components in green tea, such as polyphenols, amino acids, and vitamins, which results in the loss of nutrients and the generation of harmful substances.

Tips for Storing Green Tea

1. Avoid Moisture

Green tea leaves are porous and hygroscopic, so they have a strong tendency to absorb moisture and become damp. When storing green tea, a relative humidity of around 60% is ideal. Above 70%, the tea will absorb moisture and develop mold, eventually becoming acidic and spoiling.

2. Avoid High Temperatures

The optimal storage temperature for green tea is between 0 and 5°C. High temperatures can cause the degradation of amino acids, sugars, vitamins, and aromatic compounds in the tea, resulting in a decline in quality, aroma, and flavor.

3. Avoid Sunlight

Sunlight accelerates the oxidation of pigments and esters in green tea, breaking down chlorophyll into demagnified chlorophyll. Storing green tea in glass containers or transparent plastic bags exposes it to sunlight, causing chemical reactions that degrade the quality of the tea.