By Robert Nordstrom

Tea is a botanical, and therefore perishable, product. So, what is the relationship between tea’s age and its taste? In the second of this two-part series, WTN asks experts how tea production, packaging and storage affect its quality.

Devan Shah, owner and CEO of International Tea Importers, said simply, “Good teas age better. A Darjeeling reaches its peak nine to 12 months after its production date. It will take on a woodsy flavor after three or four years of storage, but a good tea is always good.”

Controlling exposure to moisture is the key factor in keeping tea fresh, according to Nigel Melican, managing director of Teacraft and Nothing But Tea. He said tea can have a long and stable shelf life if it is has a 4- to 6-percent moisture content when packed, if package integrity is maintained and atmospheric conditions during storage are suitable.

How fast a tea deteriorates hinges on several factors: time, moisture, light, temperature and oxygen, Melican explained: “Tea is hygroscopic and will absorb moisture from the air when the air is at a higher humidity level than the tea’s equilibrium relative humidity (ERH), until it attains a new equilibrium. Tea is manufactured at 3 percent moisture content. Generally speaking, at normal kitchen temperature and humidity, the ERH will lead to a moisture content of around 8 to 10 percent.”

When tea is stored in a sealed pack at a constant 3-percent moisture level, deterioration is very slow – even “decades” Melican claimed. “I have opened dry tea samples at 2.5 percent (moisture content) that I manufactured personally in Pakistan 12 years ago … and they were as fresh as the day they were made.”

Michael Spillane, owner and president of the G.S. Haly Company, said that, generally speaking, the tighter the leaf is rolled, the longer the shelf life, which is also affected by the season during which the tea was picked. For example, a First Flush Darjeeling picked in March will have a shelf life of six to seven months, whereas the same tea picked in June will last a year.

Traditional MedicinalsVice President of Research and Development Josef Brinckmann added that post-harvest storage and handling are critical to tea freshness.

“Our experience,” he said, “is that bulk tea-bag-cut green tea leaf, when stored properly in tightly sealed and lined drums that protect against light, heat and moisture, and packed and sealed into lined envelopes, will conform to the pharmacopoeial quality standard shelf life of three years.”

Leaf size itself affects the aging process, however, according to Jon Stout, chairman of the Golden Moon Tea Company. He warned that tea bags’ shelf life is shorter than that of loose-leaf tea because the fannings dry out faster. In addition, the oils in the broken leaves tend to evaporate, which causes “a dull and tasteless tea.”

“Black tea … has a longer shelf life than green tea,” Stout explained, “but all loose-leaf tea, properly stored, will maintain freshness for a long time. … Black tea stored in a bag inside a sealed opaque canister may keep for two years.”

Spillane summarized the conditions that affect tea freshness as follows:

• Moisture – At 8-percent moisture content, tea begins to lose freshness.
• Air – Carries moisture and contaminates, and must be controlled.
• Heat – Flattens the flavor profile, and if tea is exposed to heat above 85 degrees for a prolonged period, it may develop mold.
• Light – Causes fading in leaf color and is a source of heat.

Given these variables, storing tea in an air-tight container placed in a dry, cool, dark location will add to tea’s shelf life.