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Introduction to Brewing

Introducing the underlying chemistry in brewing beer, tea and coffee
At 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
Gladstone 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.
The 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.
For 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.
This section should certainly quench your thirst for knowledge!

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 aid the process.

For example, “a beer-making kit” typically includes a fermenter, a valve, 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 a spoon as part of your essential kit.

So, the kitchens of connoisseurs of a good brew can sometimes resemble an organic chemistry laboratory (indeed, there are some products that are a hybrid between laboratory glassware and modern drinkware). A modern organic chemistry laboratory, like our professional standard teaching laboratories at York, will have standard kits 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 specialized pieces of equipment, such as a rotary evaporator (for evaporation of solvents from samples), a Büchner funnel (used infiltration), 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 the 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.)
Scientific equipment is constantly being refined and nature is a constant source of inspiration, even for pipettes. The sex organs of liverworts have inspired a design for a plastic pipette that can pick up and transfer precise amounts of water – the shape of a ‘dipper’ is designed so that the water is gripped by surface tension!

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. Alternatively, it may be something you remember from your school days, perhaps the Bunsen burner, so popular it has its own celebration day!

This is an additional video, hosted on YouTube.

Also, as a beginning-of-the-week teaser, see if you can identify the 6 pieces of scientific equipment in the collage in the downloads section below and post your answers.

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Exploring Everyday Chemistry

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