Fashioning flawless flat whites and pulling silky espresso isn’t all about rocking a flannel shirt and cultivating a finely kept beard. In fact there’s a lot more maths and science behind the perfect shot, as Kathryn Lewis discovered when she went back to school to master the barista basics at Bristol’s Extract Coffee Roasters
Not all coffee is equal
You need to get to know the mighty bean before you start brewing. There are around 125 species of coffee that grow across the world, yet just two types (arabica and robusta) make up 98 per cent of the coffee used in our regular caffeine fix.
Robusta, often found in commodity coffee, is more bitter and less complex. Arabica, on the other hand, harbours sweeter, fruity and more floral flavours making it the green bean of choice for speciality coffee roasters such as Extract.
Roasting coffee is like cooking steak – sort of
Freshly roasted coffee can be too fresh. During the roasting process, carbon dioxide gas builds up and – like leaving a good steak to rest – a few days are needed to let this dissipate.
If you’re brewing filter style, you’re usually good to go after a couple of days, whereas espresso is best at least five days post roasting. Whatever the method, speciality coffee should be ground to order and savoured within three months of the roast date (which you’ll find stamped on the bag).
There’s a recipe for the perfect shot of espresso
To get the best out of carefully-roasted speciality beans, baristas will follow an exact recipe which takes mass (weight of coffee), yield (volume of espresso brewed), grind size (how finely the coffee beans are ground) and time (how long the espresso takes to pour) into account.
The exact calculation in the quest for the extraction sweet spot will change depending on the beans and other variables such as temperature, pressure, and even the weather. An under-extracted espresso will taste sour and thin, while an over-extracted espresso will be bitter.
Order your latte extra hot? You’re not going to achieve that velvety foam atop a flat white if you’re heating milk above 70°c. High temperatures will not only quash your latte art efforts but will also alter the taste of the milk (and therefore the coffee).
Unfortunately for calorie counters, milky masterpieces aren’t created using skimmed milk either. The best latte art (swan, rosetta, tulip etc.) use semi-skimmed or whole milk as the fat allows the bubbles to slide over each other and create a more dense steamed milk foam to work with.
Cleanliness is king
No one likes cleaning but failure to keep your ‘spro machine spick and span can result in bitter consequences. Dirty baskets (the part of the group handle which holds the ground coffee) can cause coffee to taste bitter and earthy – keep it nice and shiny for a cleaner tasting cup.
Inspired to become a pro barista? Get the deets on Extract’s next Foundation Barista Skills course here.
Ever wondered what it's like to roast speciality coffee? We got the low-down from Ashlee Eastwood-Quinn, head of coffee at Bristol's Extract Coffee Roasters