Q: Does tea lose its health benefits if it’s been stored a long time?
Answer : Selena Ahmed, a Tufts postdoctoral fellow researching the chemical ecology of tea, responds: “Some tea phytochemicals— the compounds that may have health-protective effects in humans—are more influenced by production, storage and preparation than others. The primary phytochemicals responsible for the health claims of green tea, called catechins, are found in the highest concentrations in fresh leaves. These compounds decrease over time from harvest. However, processing freshly harvested tea leaves into green tea through heating, rolling and drying helps stabilize and even increase the shelf life of catechins.
“Tea phytochemicals undergo various reactions during storage as the leaves interact with ambient oxygen and moisture and respond to fluctuations in light and temperature. Catechin levels are reduced significantly within six months of production.
“For example, the most abundant green tea catechin, called epigallocatechin gallate, has been shown to decrease 28% during six months of storage in home-like conditions, while the second most abundant tea catechin decreased 51%. Thus, it’s best to drink green tea as fresh as possible to enjoy the sensory and potential health benefits of these phytochemicals. Storing tea in sealed packaging in cool, dark conditions helps increase shelf life.
“While fresh may be best for enjoying many types of teas, that’s not always the case. Some pu’er teas from China are considered to improve in taste with storage, much like a fine wine. In fact, the degradation and oxidation of catechins during storage of pu’er teas result in the formation of new phytochemicals, which have come to be highly valued by tea drinkers for their rich, earthy taste and probiotic health properties.”