Good questions, silverneedles. I've excerpted the paper's abstract below.
abstract wrote:Hicks, M.B., Hsieh, P., & Bell, L.N. (1996). Tea preparation and its influence on methylxanthine concentration. Food Research International, 29, 325-330.
The amount of tea or coffee estimated from the number of cups consumed is frequently used as an indication of caffeine consumption in epidemiologic studies. However, this alone may be an inadequate indication of intake since drinking practices of tea varies. In this study, methylxanthine (caffeine, theobromine, and theophylline) contents in three brews of four types of tea (black, oolong, green, and herbal) in both bangs and loose leaf forms were investigated to determine the actual amount of methylxanthines present in tea as a function of different brewing methods. On a dry leaf weight basis, total caffeine after three brews was highest in black (32.8 mg/g) and green (36.6 mg/g) tea leaves and lowest in Formosa oolong tea 2 (23.8 mg/g). Total theobromine was highest in black teas (1.64 and 1.69 mg/g) and least in oolong teas (0.65 and 0.71 mg/g). Caffeine and theobromine were not detected in either herbal tea samples, and theophyline was not detected in any tea tested. The overall average caffeine released in the first through third brews were 69%, 23%, and 8% respectively. Three cups of tea brewed using three tea bags (Western culture) have approximatedly twice the amount of methyxanthines as the same volume prepared by three successive brews of loose tea leaves (Asian culture). These differences should be accounted for by the epidemiologic studies evaluating the effect of methylxanthines on health.
Hicks and crew used 8 different types of teas: 2 black teas (Lipton tea bags and loose Asian black tea leaves), 2 different loose Formosan oolongs, 2 green teas (Lipton green tea bags and Korean green tea leaves) and 2 herbal 'controls (Celestial Seasoning's "Lemon Mist" and International Bazaar's "Cinnamon Apple.")
For the bagged teas, 1 bag was placed in a beaker and 177ml of boiling water was poured over it. The tea was allowed to brew for 5 min and allowed to drain into the tea for an additional 30 sec.
For the loose teas, 2.3-2.5 grams of leaf were measured out and prepared in the same way. After a 5 minute brew, the leaves were placed on filter paper and allowed to drain into the tea for an additional 30 sec. The two oolong samples, however, were prepared in a ratio according to the package instructions: 3 grams in 150ml of boiling water. This worked out to be 3.5458 g/177ml.
The total amount of caffeine in each tea ranged from 23.8 mg per g of leaf to 36.6 mg per g of leaf. The full numbers are given in the article.
The infusion intervals and temperatures would be pretty undrinkable to me too...Hicks and crew weren't testing palatability, but rather showing for the first time that caffeine infusion does not follow a linear pattern.