omegapd wrote:This brings up something I've thought about before but never asked...
If all tea comes from the same plant, why would there be a difference in caffeine levels? Would the way tea is processed have anything to do with caffeine levels?
Well caffeine is always a complicated question. There really are two parts to this question though. Caffeine in the leaf and caffeine in the beverage.
Caffeine in the leaf: The amount of caffeine in a the leaf itself starts from the actual plant itself. The caffeine is a natural product in the plant, which through cultivation, breeding, fertilizing, etc. can produce different amounts. One thing in particular that I have heard is that the heavy fertilization that the Japanese use for their tea tends to increase the caffeine content.
Caffeine in the beverage: Extraction of caffeine from tea is very temperature dependent. Black teas are steeped at boiling temperatures where greens use colder water. As a result even if the leaves had equal amounts of caffeine just prior to brewing the black tea would extract more. Then there's also the extraction time to take into effect, yadda yadda yadda.
To put it simply unless you're doing a very very detailed controlled study of the caffeine content, it's almost a random crapshoot.