What's in a Coffee?

Most of us have a favourite style of coffee and every cup will taste different because of the roast of the coffee bean, the grind, the amount of bean used, the water, the temperature and many other factors. At home, you may have tried to reproduce the coffee goodness from the coffee houses, but do we actually know the best method to use in order to elicit the captivating flavours perfectly? Here are some pointers for how to make these excellent coffees.

Capuccino, Mocha, Latte or Espresso?

Cappuccino: This drink consists of equal parts of steamed milk, frothed milk and espresso. The milk is poured on top of the coffee shot and dusted with nutmeg, cinnamon or chocolate powder.

Mochas: The easiest way to do this is to make it with quality hot chocolate, add a shot of coffee with steamed milk poured in and top with whipped cream, then lightly dust with chocolate powder. It looks great in a clear glass mug with a long-stemmed spoon.

Lattes: Foam and steam milk to 75 °C. The ratio is worked out as 50% coffee and 50% milk. Slowly pour the milk down the side of the coffee cup or glass so it infuses with the coffee shot. The main difference between a latte and a cappuccino is a latte blends the milk and coffee together, whereas the cappuccino keeps the two apart.

Espressos: Using a finely ground good quality coffee bean and a high pressure espresso pot gives a coffee shot with a golden-brown foam on top, to be served in an espresso cup to keep the coffee warm as it is being drunk.

Steaming milk involves introducing hot water vapour into cold milk until it reaches the ideal temperature for the drink. It is not as simple as it sounds as different milks (with different amounts of proteins, carbohydrates, and fats) require different amounts of steaming time. For example, fat molecules can stabilise the formation of foam by surrounding the air (injected during the steaming) and entrapping it in a bubble – milks with higher fat content lead to stable foams at temperatures below room temperature, while milks with lower fat contents (like skimmed milk) are better at stabilising foam at higher temperatures. The temperature is key as too high a temperature can scald the milk, which denatures the enzymes and causes curdling (as denatured milk proteins clump together).

At the end of the day, making coffee correctly is all up to you and the way your taste buds take to the coffee taste, or indeed, if you like coffee in the first place! A survey of our second year York undergraduate chemists showed that water was their most popular non-alcoholic drink, followed by tea then coffee. They preferred black tea to green or herbal teas, and almost all put milk in their tea in preference to adding lemon juice or drinking it black. By far the most popular coffee was latte followed by cappucino and only 5% of the students knew what bulletproof coffee was.

So, what is your favourite non-alcoholic drink, and why? Do you have a particular routine (such as a Turkish coffee approach) for making your favourite brew and/or do you use any unusual ingredients? For example, I wonder how many of you enjoyed an eggnog latte at Christmas?

For those of you with an interest in Latte Art why not post a picture of your creation #FLchemistry (on Twitter or Instagram), showing the design you have created by pouring steamed milk into a shot of espresso?

Rather than a handful of words, why not use over 100?

You might describe your coffee as ‘strong, black and hot’, but the Specialty Coffee Association of America (SCAA) has taken it to a whole new level. The SCAA’s Flavour Wheel provides a full descriptive glossary for both good coffee and bad coffee, and is standard-use for modern coffee tasting (or coffee cupping). To describe your coffee, start at the centre and work outward. The most general taste descriptors are near the middle, and they get more specific as the tiers work outward.

Why not give it a go and share your findings, so we can discuss and compare your results?