It’s cold so let’s talk about temperature, in brewing coffee. Ever noticed that it's harder to extract more complex flavours from your filter coffee in colder weather? In this quick post, Extract's Head of Product, Dan Lacey explains why that happens and how to avoid an under-extracted brew.
Brewing filter coffee is fraught with variables, some are easily controllable like coffee choice, brew method, (immersion, gravity filter, manual pressure) filtering your water and your recipe - the coffee to water ratio which will mostly dictate strength.
Grind size is somewhat controllable - you can adjust them to slow down or increase the flow or increase/decrease surface area of the coffee, though we all know grinders aren’t always the most stable or consistent of tools. The finer you grind the more fines you get which can stall your brew by clogging your filter and cause over extraction.
Turbulence is crudely controllable, think about the water interacting with the coffee - from an aggressive or gentle pour, stirring/agitating the coffee with a spoon or pressure, like an Aeropress.
Temperature of water we think of as a choice, we can set the boiler or maybe our kettle at home, or use a thermometer. In reality we are never brewing anywhere near as hot as we think we are.
Let me try and explain how lack of temperature control negatively impacts your brew
- When brewing coffee using a pourover method, like V60 or Chemex, we use small amounts of water, usually between 250-500ml in total. That isn’t a lot of thermal mass, so it cools quickly.
- We add small amounts of water at a time to enable an even extraction, about 50-100ml per pour.
- We decant our water into coffee kettles or jugs that are easy to pour carefully from - but in a thin stream that has lots of contact with the air and cools quickly.
- Small, open topped methods like a V60 or Chemex allow heat to escape.
- We don't always preheat our brewing equipment properly.
- We don’t heat our stirring spoon!
I first suspected that temperature was a problem in manual brewing when measuring the taste balance and extraction of an aeropress when a good friend, lovely man and fellow SCA trainer, Alex, was practicing for the UK Aeropress championship back in 2016?? (I think).
We were changing variables and tasting the resulting changes, but struggling to get an increased extraction without bitterness. I suggested checking the temperature, not at the boiler, but in the brewing chamber.
Turns out using 96° water, into a preheated pouring kettle, into an aeropress gave 86°- 88° water at the start of the brew which decreased with time and turbulence (especially if you, like me, like to stir it up to fully saturate the grounds).
For reference SCA guidelines state to use 93° +/- 3° water for brewing filter coffee
We tried preheating the aeropress, but plastic doesn’t hold much heat and the hottest we got was 91° - using 98° water directly into the brew chamber with minimal stirring.
I like to think those learnings on temperature helped Alex make it to the semi finals that year but more importantly it’s helped me brew fuller, tastier coffees without having to grind finer and risk clogging up my brews and over-extracting the coffee.
4 golden rules for brewing filter coffee in cold weather
- Preheat the hell into your cups, cafetieres and kettles.
- Use hotter water than you think you can.
- Get the coffee hot and wet, keep it wet and hot
- Have fun!
I hope that this has been useful and help you all enjoy better brews during the cold weather. Until next time friends.