How to Keep Green Tea Fresh: Factors and Techniques
Green tea is beloved for its unique qualities of “clear soup, green leaves” and “fresh, mellow and sweet.” To ensure the best sensory flavor and nutritional value of green tea, it’s important to store it properly.
Factors Affecting the Storage Quality of Green Tea
- Moisture: Water is the basic factor affecting the quality and freshness of green tea after delivery. When the water content of green tea is higher than 7%, it’s difficult to maintain the quality of green tea with other preservation technologies or packaging materials.
- Temperature: Temperature is the key factor affecting the change rate of green tea quality, including storage temperature, circulation and transportation temperature. The commonly used storage temperatures are cold storage (0-10 ℃) and freezing (- 18 ℃).
- Light: Light promotes the decomposition of chlorophyll, which is a direct factor affecting the color of green tea.
- Oxygen: Oxygen is an important factor affecting the oxidative degradation of green tea polyphenols, vitamin C, fatty acids and other substances. Exposure to high oxygen environment will directly lead to the loss of green tea flavor and nutrients.
Common Storage and Fresh-Keeping Techniques of Green Tea
- Drying preservation technology: Water control is a prerequisite for the quality and freshness of green tea after delivery. The water content of dry tea should be controlled below 6%, and desiccants (lime, charcoal, silica gel, etc.) can be added in the storage to reduce the water content of tea. However, this technique has some shortcomings such as low water absorption and easy failure.
- Low temperature refrigeration technology: Low temperature cold storage technology is the most widely used green tea preservation technology. Large capacity refrigerators and small capacity freezers are used to achieve green tea preservation. It’s important to gradually restore the room temperature of green tea taken out of the cold storage or freezer in the buffer space before packaging and transportation to avoid moisture condensation and accelerate the aging of green tea.
- Deoxygenation and preservation technology: Controlling oxygen content is an important means for green tea preservation. The commonly used deoxygenation preservation technologies include vacuum technology, deoxygenation and nitrogen charging technology and deoxidizer preservation technology. It’s important to consider the tea type, packaging materials, purity of nitrogen filled, and the quality ratio of preservatives to green tea to ensure the best fresh-keeping period of preservatives.
- Specific packaging materials: Multi-layer composite packaging materials composed of high-density polyethylene, polypropylene, and low-density polyethylene film should be selected to block the contact between green tea and external environmental factors to the greatest extent. The packaging materials should have good oxygen resistance, moisture resistance, fragrance retention, and light shielding properties. Water vapor permeability and oxygen permeability are two important indicators to evaluate the barrier performance of tea packaging materials. Aluminum plating and perspective window packaging are not recommended.
For example, after 18 months of storage at 15 ℃ and 65% relative humidity, the green tea soup in traditional packaging bags turns yellow and has a stale taste, while the quality of green tea packaged with high humidity resistance and strong oxygen resistance materials remains largely unchanged.
In summary, maintaining the freshness of green tea is crucial for preserving its flavor, aroma, and health benefits. By understanding the factors that affect green tea’s shelf life and implementing proper storage techniques, such as using airtight containers and avoiding exposure to heat, moisture, and light, you can ensure that your green tea stays fresh and delicious for longer. Whether you’re a casual tea drinker or a connoisseur, taking care of your green tea can help you fully enjoy its unique taste and benefits.