The ability to control coffee extraction is both one of the best, and one of the trickiest, things about drip brewing. There are so many elements to consider: grind size, coffee to water ratio, water temperature… But get it right, and you can craft a delicious cup of coffee.
One thing that can help you understand extraction, and how to use it to brew better coffee, is the theory of the three phases of drip/filter brewing. I spoke to Patrik Stridsberg, Co-Founder of 3TEMP, and London-based coffee professional Will Corby to find out more about it.
1. The Pre-Brew (The Bloom)
The pre-brew, or the “bloom,” is the first stage in manual or drip brewing. You pour a small amount of water, just enough to wet the grounds, and wait for around 30 seconds. And there’s one simple reason we do this: carbon dioxide.
During roasting, this gas becomes trapped inside the coffee bean. (Generally speaking, the lighter the roast, the more is trapped; with dark roasts, second crack releases more of them.) Degassing occurs slowly after roasting, and also during the brew process, as the remaining gas is released when grounds are hit by hot water. This is what creates the bloom. And as you might imagine, the more gas escaping, the bigger the bloom will be.
The bloom makes your coffee better in two ways. First, carbon dioxide has a sour taste that you don’t want in your cup. (Remember, there’s a difference between sparkling acidity and sourness.)
Secondly, as your coffee grounds expel gas, the force of that gas will also push water away from the coffee, disrupting extraction. You want this to happen during the pre-brew phase rather than the main extraction, so that you’re not getting inconsistent flavors in the cup.
During this next phase, you can start to control the flavor of your brew. This is because different chemicals are extracted at different stages: first, you’ll get fruity acids, then sweetness, and finally bitterness. (It’s worth noting that not all acids are those fruity, desirable ones: for example, caffeoylquinic acids create astringency/dryness and bitterness. When we talk about acidity in this article, we’re only referring to those chemicals that create an acidic taste.)
Since different chemicals are extracted at different points, you can manipulate the brew to create your desired cup profile. And the best way to do this is through controlling the water temperature and brew time.
Generally speaking, the ideal brew temperature is between 91°C and 96°C (196 °F and 205°F). Roast level, flavor profile, solubility, freshness, grind profile… all these can play a role in determining the best temperature.
Patrik tells me that another important point to consider at this stage is “pulsing”. This is when brewers use multiple small pours. For manual brewing, to achieve consistency across different brews, some people recommend decreasing the number of pours – it removes the number of variables that baristas have to control.
Yet Patrik argues that pulsing is important. In fact, he built it into his company’s brewer, the Hipster, as a programmable stage because he believes it improves the consistency and efficiency of extraction. He explains to me that fewer, bigger pulses will shorten the extraction time, while more frequent, smaller pulses will lengthen it and leave the coffee bed even. The best number of pulses will depend on the coffee itself and the grind size.
3. The End Phase
The “end phase” refers to the final 40% of the brew, Patrik tells me, and you need to control it carefully. Remember that the last chemicals to extract are the ones responsible for bitterness and other unpleasant tastes. Over extraction here could mean disaster for your brew.
Patrik advises being careful with brew time and also temperature. A lower water temperature at this stage will lead to less extraction. In turn, this will create an overall more balanced, sweet, and acidic cup of coffee.
If you’re brewing a pour over, you don’t really have to think about this: the water temperature will naturally cool as time passes. However, if you’re using a mechanical brewer/batch brewer, you’ll want to consider the brew temperature when programming it.
Patrik explains that the default settings on his company’s Hipster are 97°C (206.5°F) for the pre-brew, 94°C (201°F) for the extraction, and 89°C (192°F) for the end phase – a whole 5°C less than the extraction phase.
Although he recommends adjusting the settings for different coffees, he tells me that this pattern of decreasing temperatures is best for ensuring sweet, fruity, and balanced brews.
Whether you’re preparing a single cup at home or a large batch in a café, understanding every aspect of the brew process is important. Temperature variations are one of several critical elements that need controlling.
Fortunately, knowing the three stages of drip brewing can help us to manipulate our
temperature and create that delicious cup of coffee we’re craving.
*Commissioned article originally published on Perfect Daily Grind