Chemistry of Tea: Caffeine, Amino Acids, and Vitamins
Episode #3 of the course The science of tea by Lukasz J. Binkowski
Welcome to the third lesson of the course.
Today, we will discuss the composition of tea. This topic is important not only because it’s the chemical composition that creates the unique taste and aroma of tea, but also because it brings great benefits to human health.
There is a difference between the composition of the leaves and the composition of the infusion. In general, everything depends not only on the type of tea but also on the temperature of the water, water hardness, and the time during which the infusion has been brewed. We’ll concentrate on the composition of the infusion and leave the rest for the food chemists.
Caffeine
Tea leaf contains numerous elements, but caffeine is one of the most well-known. Caffeine found in tea is often called theine, but it’s basically the same compound.
As you may know, it is responsible for stimulating the nervous system. However, coffee usually influences the nervous system more intensely and faster than tea because:
• The concentration of caffeine in a cup of coffee is between three and four times higher than in tea.
• Caffeine in coffee is usually not strictly bound to any compound, while caffeine in tea is usually bound to numerous compounds.
For the same reasons, after drinking coffee, we may feel excited for a short while, but after drinking tea, we feel energetic for a longer period. However, if the stimulating effect of tea is still too strong, you may consider drinking decaffeinated tea.
Caffeine belongs to the group of alkaloids produced by plants. The exact reason why the plants need caffeine is still rather unclear, but considering the properties of alkaloids, their main role is most likely protection against herbivores. There are also other alkaloids in tea, such as theobromine and theophylline, both with a similar pharmaceutical effect.
Amino Acids
Tea is also a source of amino acids; the most common is theanine. This compound occurs almost exclusively in tea and has psychoactive properties, since it crosses the blood-brain barrier (a membrane that separates the circulating blood from the brain).
In addition, theanine increases the intensity of alpha waves in the brain (the type of brain waves detected during wakeful relaxation). It also exerts a calming effect and reduces stress, which is another beneficial influence tea has on the body, resulting in improved cognitive skills.
Besides theanine, there are almost 20 other different amino acids in tea, but their influence on on the drinker remains insignificant due to their low concentrations.
Vitamins
Tea leaves are rich in numerous vitamins, including A, B, C, and K. However, only vitamins B and C are soluble in water, so only they are transferred after the leaves have been infused.
The types of vitamins in an infusion depend greatly on the type of tea. In black tea, for instance, only B complex is present, whereas in green tea, vitamin C may also be found. The concentrations of vitamins in the infusion are generally low and too insufficient to have any noticeable effect. Still, their overall positive contribution to the diet cannot be questioned.
The above compounds are not the only elements one may find in tea. Tomorrow, we’ll discuss a few others.
Till the next lesson,
Lukasz
Recommended book
Tea: A User’s Guide by Tony Gebely
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