Generally speaking, 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 by reducing or eliminating these factors, the tea can be preserved for a long time. To determine if the tea has expired, primarily consider its taste and infusion color.

Typically, the shelf life of Green Tea is around one year, but if improperly stored and it becomes damp causing the moisture content to exceed the standard, it may expire in as little as two months. Once opened, green tea should be transferred to an airtight container and consumed within two months if possible.

How to Tell If Green Tea Has Gone Bad

1. Smell the Aroma

Stale green tea will have odors such as mustiness, sun-dried scent, mold, or off-flavors. Deeply inhale the dry leaves or the aroma of the tea infusion; if there are noticeable stale, sun-dried, moldy, or off-flavors, it's best to find fresh tea.

2. Examine the Dry Leaves

If the tea leaves appear dark yellow and aren't crisp, it is likely spoiled. If you can only crush the dry leaves into small pieces with your fingers and the twigs do not break easily, this indicates spoilage. Unspoiled green tea, under normal circumstances, contains about 7% moisture and can be ground into powder.

3. Inspect the Infusion

The infusion of spoiled green tea will be brownish and heavy, lacking clarity. It will have a full-bodied water flavor, losing its astringency and freshness. The refreshing sensation characteristic of green tea will be completely absent.

This change in the tea's character is due to the oxidation of the main components of green tea: polyphenols, amino acids, and vitamins. These changes indicate the loss of nutrients and the formation of harmful substances.

Green Tea Storage Tips

1. Avoid Moisture

Green tea leaves are porous and hydrophilic, so they have a strong tendency to absorb moisture and become damp. When storing green tea, a relative humidity of 60% is most suitable; above 70%, mold spots may form due to moisture absorption, leading to souring and spoilage.

2. Avoid High Temperatures

The optimal storage temperature for green tea is 0–5°C. Higher temperatures can cause amino acids, sugars, vitamins, and aromatic compounds to decompose, leading to a decline in quality, aroma, and taste.

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 and exposing it to sunlight causes chemical reactions that deteriorate the tea's quality.

4. Avoid Oxygen

Chlorophyll, aldehydes, esters, and Vitamin C in green tea readily combine with oxygen in the air. Oxidized green tea will result in a redder and deeper infusion color, significantly reducing its nutritional value.

5. Avoid Off-Flavors

Green tea contains high-molecular-weight palmatase and terpenoids. These substances are very active and unstable, capable of absorbing off-flavors. Generally, the shelf life of green tea does not exceed one and a half years, but if improperly stored and becomes damp causing the moisture content to exceed the standard, it may expire in as little as two months!