Tea Shelf Life Tested
A new study tested the impact of humidity and added chemicals during the storage of dry green tea powder.
During a three month storage test, researchers found that catechin stability (including EGCG, or epigallocatechin gallate, as well as epicatechin, epicatechin gallate, and epigallocatechin) could be maintained at 43% relative humidity at 22 degrees C for three months, despite caking.
Additives and humidity reduce shelf life
Higher humidity caused chemical degradation and reduced the effective shelf life of tea.
The addition of sucrose, citric acid, and ascorbic acid to green tea powder during storage also significantly increased catechin degradation (Ortiz J, Interaction of environmental moisture with powdered green tea formulations: effect on catechin chemical stability, Journal of Agricultural and Food Chemistry, June 2008).
Green tea catechins are the primary antioxidants associated with risk reduction for many health conditions.
People using green tea powder such as matcha should buy amounts that they can use within a few months after opening.
People buying powdered green iced tea mixes may want to avoid those with sucrose, citric acid, or ascorbic acid if they want to be more certain of tea shelf life and antioxidant stability.
Or make their own green iced tea from freshly brewed varieties.
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