Tea Chemistry - Periodic Table of Videos

well in a couple of days time it's the Chinese New Year and we thought we could mark the Chinese New Year by looking at a bit of the chemistry of tea so before we start have to make some tea I will just go along the corridor to the start and Robin so we're going to make some green tea and some ordinary tea as well so we can compare them I don't really like black tea very much but I'm very fond of green tea and they're the same plant but they're just processed differently and we put some in my teacup as well I just personal uses it yet that should just keeping me going chemists never trust clinking out of beakers so we give each of them a stir and then go back to my office it's the green tea it's the ordinary tea I want to try and show you what happens when you put lemon in tea so if I cut the lemon in half and you know lemon juice is very acid so let's see what happens I will move the two together so all being well we can compare them so are you ready we will try squeezing in some lemon juice so apart from the pit going can you see that as we have added the lemon juice is gone really much lighter color and the reason for this is that tea contains molecules or chemicals that behave like circle indicators they change color when you put acids in and what happens is that the acid from the lemon juice adds a proton to the molecule of the indicator in here the one that changes color and just by adding this proton it causes the bonds in the molecule to switch around and so they absorb light in quite a different way now tea isn't doesn't give you a terribly dramatic color change compared to some of the indicators that like litmus that people have used in the lab which can go from pink to blue but it doesn't do badly there's quite a lot of argument whether chemically it makes any difference if you put the milk into the cap before the tea or you fill up the tea with the cup with tea and then add the milk afterwards and there's some people who get really passionate they will only drink tea with the milk before all the milk afterwards and they swear that there are big differences do you have a position on this I don't have any position at all I don't like milking teas so I don't enter into that debate at all the different sorts of teas that you buy are basically the same plant but they differ from the different components that there are in the tea the when you put tea in water the water the hot water extracts a huge number of different chemicals from the tea these are not pesticides and things that have been added but their actual chemicals that are created by the plant when they grow and depending where the plant grows whether it has been a sunny summer whether it's been a wet summer so that the different amounts of the chemicals changes so one of my colleagues who works here used to work for a company that sold tea and they wanted to analyze it to find out how the different sorts of tea varied so they used a machine like the one behind me which is called a nuclear magnetic resonance spectrometer NMR spectrometer which measures the different sorts of hydrogen atoms in a particular molecule now the problem with tea is it's quite easy to get a sample of tea and put it in a tube like this but this then goes inside that machine you can see a whole series of them waiting to go in there those are not tea but there are chemicals from the department but what you end up with is a really complicated picture of all the thousands of different components of tea and here I've got a real spectrum of green tea and you can see it looks a complete mess lots and lots and lots of components along here but the important thing is and what they were trying to do in their analysis was to see how the different sorts of teas varied and see if they could see a real difference between something that tasted nice and something that wasn't quite as good and although you can't necessarily identify their individual compounds you can say that some say here are due to different sorts of sugars and these are due to more complicated molecules the so so called polyphenols but even the chemists like me doesn't really know what all these compounds are though you can get an idea how one differs compared to another part of the reason why people like the red dark tea rather than green tea is the dark tea has a lot more caffeine in it than the green tea the processing of the tea concentrates the caffeine and probably the fermentation actually generates more of it now the caffeine doesn't have very much effect on the taste of the tea or of coffee and so some people find if they drink too much coffee or tea late at night they can't go to sleep and so nowadays it's quite fashionable to have decaffeinated tea or coffee the problem is that the traditional way of removing clean from coffee or tea is using dry cleaning fluid dry cleaning fluid is a carbon compound of carbon chlorine and hydrogen which sometimes can leave quite unpleasant residues in the coffee beans or the tea leaves and so nowadays the preferred method for removing caffeine from tea and coffee is by using highly compressed carbon dioxide so called supercritical carbon dioxide which can dissolve out the caffeine without dissolving very much else from the material and co2 is completely harmless in terms of health people drink tea drink water with co2 in it every day and so it doesn't leave any residues at all and the process is rather better with coffee because with coffee it just removes the caffeine with tea it does review remove some of the flavor components and they have to be put back in again afterwards and the caffeine that you extract can be sold on to people who make caffeinated drinks the ones that give you energy and keep you awake and so this is a good process because you put calm dioxide of your tea or coffee and make a more valuable decaffeinated product you have some caffeine to sell to somebody else Noreen had naturopathy she gensphoto Sadashiv in satsang Julian Union that eventually

Channel: Periodic Videos

Views: 526,088

Rating: 4.9238157 out of 5

Keywords: tea, chinese, new, year

Id: EFPosXIYGP0

Length: 8min 43sec (523 seconds)

Published: Fri Jan 23 2009

Reddit Comments

[u/CogitoNM]

Looks like a Mad Scientist, but his videos are rather fun to watch. Just figured some might like this one here. Hasn't been posted in 3 years, so I hope enough time had elapsed.

[u/Selderij]

While many of the points are cool, the part about black tea having much more caffeine or the processing affecting it is false.

[u/mindofmanyways]

Thanks for showing this. No one goes back three years in a forum to find something good. As a result, I've watched dozens and dozens of Periodic Table videos and I love them.