Skip to 0 minutes and 6 secondsAt the end of a hectic day, how relaxing to sit down with feet up and a refreshing brew. Former British Prime Minister, William Gladstone, was clearly a fan when he said, 'if you are cold, tea will warm you. If you are too heated, it will cool you. If you are depressed, it will cheer you. If you are excited, it will calm you.' But it is not only
Skip to 0 minutes and 26 secondsGladstone that enjoys a brew: Around 2 billion cups of coffee are consumed worldwide every day and tea remains the most consumed drink in the world, after water. In the UK alone, the tea market is worth around £700 million per year. Our tour of beverages concentrates on the chemistry of beer, tea and coffee. We will start by looking at the beer-making process, from milling to maturing. Of particular interest will be the key flavour components. We will see how a compound found in hops, undergoes a rearrangement reaction during the brewing process, to form compounds called isohumulones - these give a pint of bitter its name.
Skip to 1 minute and 9 secondsThe bitterness of beer is measured according to the International Bitterness Units scale, with one IBU corresponding to just one part-per-million of isohumulone. We will then look at brewing a cup of tea, and what organic compounds are present, including polyphenol antioxidants. Tea is rich in antioxidants including catechins, which generally give a bitter taste to tea. Hardly a week goes by without a claim that drinking a cup of tea is good, or bad. So we will look at the underlying chemistry and the structures of the organic compounds involved in these claims. Finally, we will explore coffee, which contains over 1000 aroma compounds. Again, the reported health effects of drinking coffee can be conflicting, including that for caffeine.
Skip to 1 minute and 54 secondsFor example, a large US study found that women who drank two or more cups of coffee a day were less likely to get depressed. Caffeine is known to improve memory and the speed with which our brains process information - it increases the production of neurotransmitters such as dopamine. It also increases breathing and heart rate, resulting in a short burst of energy. The average daily intake of adults is around 200 mg of caffeine - equivalent to two mugs or four cups of coffee. For those of you who prefer coffee without caffeine, we will investigate how decaffeinated coffee is prepared - the use of supercritical carbon dioxide is particularly effective, removing 97-99% of the caffeine from the beans.
Skip to 2 minutes and 38 secondsThis section should certainly quench your thirst for knowledge!
Introduction to brewing
Welcome back to the course and our third week of study, which explores brewing!
Brewing is both an art and a science. For a pleasing brew, whether it be a pint of bitter, or a cup of filter coffee, there are various devices to use to aid the process.
For example, a beer making kit typically includes a fermenter, a valve and tubing, a funnel, thermometer, hydrometer (that measures the specific gravity (relative density) of liquids), a spoon, bottles and caps. Those of you who make drip or filter coffee will need filter paper, a kettle, a balance, a grinder and spoon as part of your essential kit.
So, the kitchens of connoisseurs of a good brew can sometimes resemble an organic chemistry laboratory. A modern organic chemistry laboratory, like our new teaching laboratories at York, will have standard kit ranging from mechanical stirrers to balances, thermometers, and lots of glassware. This includes Quickfit glassware, required, for example, when carrying out a distillation.
Then there are the more specialised pieces of equipment, such as a rotary evaporator (for evaporation of solvents from samples), a Büchner funnel (used in filtration) and glassware, such as Kipp’s apparatus (for making small volumes of gases) and a Kjeldahl flask (round-bottomed and long-necked to trap splashes from material being boiled for analysis). Indeed, some pieces of laboratory glassware are so intricate and beautifully designed that they may not be out of place in an art gallery! (At York, we are fortunate to have our own chemistry glassblower.)
So what is your favourite piece of chemistry-related equipment or glassware, and why? This may be something in your home, perhaps a test tube spice rack or a mortar and pestle, or for those of you doing a course or job involving practical chemistry, something from your laboratory.
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