Caffeine is nature's own insecticide! It is what protects plants from attack by pests. Unfortunately—though not always-- it can also have adverse effects on humans. To make matters worse, it is found in some of our most favorite foods and beverages—coffee, tea and chocolate.
Everybody knows that tea contains caffeine. As a matter of fact pound for pound tea has significantly more caffeine than coffee. In the cup, however, it has less than 50% the caffeine content of coffee. The amount of caffeine in any given tea is determined by many factors, however the category (black, green, white, etc.) has little, if anything, to do with it. That is to say the color of the leaf and the amount of oxidation do not really factor into the equation. The primary determining factors are:
1. Location of the pluck—the newest shoot and the next two leaves plucked at
first flush are the highest in caffeine (i.e. the top two leaves and a bud)
while older leaves have less.
2. Season of harvest--first flush would be highest. When the plant comes out of dormancy it is the most vulnerable to attack, so nature has given it this powerful natural insecticide—caffeine!
3. Varietal & cultivar--Camellia sinensis var. assamica has more caffeine than Camellia sinensis var. sinensis. When it comes to cultivar, it is rather hard for the average tea aficionado to know. There are literally tens of thousands of cultivars. Some we know have been tested by scientists for caffeine content and included in published studies but the vast majority have not.
4. Manner of production.
Given all of the above it is generally understood that white tea has more caffeine than most other teas. Good quality white tea is plucked at first flush--the very first growth of the season. The pluck is limited to the top two leaves and a bud or just the bud--the leaves with the highest caffeine content!
Oolong teas are the lowest in caffeine content. Oolong leaves, though still young, are allowed to grow larger than leaves for green, black or white teas, so as to allow the salutary compounds in the leaf to become more fully developed. As such, they are plucked a little later in the season. In addition, oolong teas such as Wuyi and Phoenix, are twisted after fermentation causing the juices to coat the surface of the twisted leaf. During the baking process these juices (and thus the caffeine content) crystallize on the surface of the leaf. In the traditional method of oolong preparation the tea is given a quick rinse in hot water prior to steeping. Inasmuch as caffeine is a readily soluble substance, this step effectively washes away a good portion of the caffeine content.
Numerous studies have been done on the caffeine content of tea, but there is still a long way to go before we know everything we need to know. Most of the studies to date have used low quality grocery store variety tea bags. The problem with that is that quality is an important factor in every aspect of tea, from flavor to health benefits! Studies that use only low quality tea do not provide us with the whole picture. The catechins in tea are very unstable and their effectiveness is compromised when mishandled and/or exposed to the environment. Light, heat, humidity, aromas, age…all of these take their toll on tea. Every time you break a tea leaf another surface is exposed. What’s more, the highest concentration of catechins is in the first two leaves and a bud. A recent study in Taiwan analyzed the catechin content of tea leaves by their twig position. It showed that each of the youngest three leaves contains between 38 and 43mg of flavonoids per gram of tea liquid. That is 1900 to 2150 mg per 100 ml. The major brands of mass produced teas utilize machine harvesting and processing for the most part. These harvesters uniformly chop off the top two inches of the tea bush—that’s leaves, stems, flowers, everything! The quality of t he product comes nowhere near the traditional method of hand plucking and processing. So, you might ask, what does this have to do with caffeine?
The answer to that question in Part 2 of our discussion about Tea & Caffeine