Discussing Brew Methods

January 28th, 2012

This post is a follow up to the poll I posted a little while ago. I was wondering if my own thinking about brew methods mirrored others, or whether they were different. I admit it was something of a flawed poll, but I wanted to use it as a stepping stone to this larger post. (This is a long blog post.)

My thinking in this revolves around the fact that we often talk about how a certain brewer could highlight certain aspects of a coffee’s taste and quality. I want to explore this idea in a little more depth, because this is such a fuzzy idea that I don’t think it is particularly helpful.

I’m going to avoid talking about specific manufacturers of equipment, primarily because I have a conflict of interest in this area.

I should also point out that a great deal of this post can be written off as anecdotal, and I’m more than happy to discuss contradictory experiences or opinions.

What do you want to highlight?

I figure the best place to start is by taking a slightly more objective look at the potential characteristics of a coffee that we might be highlighting. Most scoresheets used for cupping exist to assess green coffee but there are sheets used for other purposes. There are certain common attributes that are assessed:

- Sweetness
- Acidity
- Mouthfeel/Body
- Balance
- Aroma
- Flavour
- Finish

When brewing a coffee we should be thinking about how the process impacts each of these attributes and presents.  How do we influence each of these factors with our equipment and technique?  This is a more difficult question to answer, because it is all so interconnected.

Most of the above attributes are primarily linked to extraction.  The coffee itself is obviously the determining factor of how much sweetness is available, or how much positive acidity is available for us to capture in the cup but the quality and quantity of each of these in the brew is tied to extraction.

Extraction remains a sticky topic.  I believe that uniformity of extraction is important, and also that whatever people consider their desirable range of extraction is tied heavily to the grinder and its particle size distribution.  Regardless of what your desired level of extraction is, there are certain factors that have a strong influence when we are brewing.  Two of these are deeply interconnected:

- Grind Size
- Contact Time

The first two have the most obvious connection – the grind size determines surface area of coffee exposed and the rate at which solubles extract, and with all brew methods we must be careful to balance our grind size and our contact time.  You can brew a french press at a number of different grind sizes and have good results as long as the contact time is appropriate.

The moment you read that another thought might pop into your head – which is that surely brew time has an effect on brew temperature.  If I grind very coarsely, requiring a longer steep in my press pot, then surely the average temperature of the brew will be much lower?

Temperature is still something that we don’t really understand in brewing coffee.  We’re happy to talk about espresso brewing temperatures, yet references to the brewing temperature of drip coffees is remarkably absent from published recipes or discussion.  Temperature has a brute force effect on extraction – it supplies energy required for a soluble to enter a solution, so generally the more heat you have the more extraction you have.

Along with overall extraction we have the extra effect of thresholds of temperature required for certain compounds to be extracted.  The best example of this are the negative, bitter qualities we extract from even light roasted coffees when the brew temperature is very high, up towards boiling point.  Brewing at lower temperatures – 80C/175F for example – allows a reasonable mechanical extraction of the coffee, resulting in reasonable body, simplistic sweetness but overall a cup lacking complexity and character.  This experiment also highlights the unusual effect of temperature on acidity.  Brewing at temperatures like these doesn’t result in the sour cups we might come to expect, instead the acidity is notably absent – requiring more temperature to be fully extracted.

Back to Brewers

Temperature often seems to be a separate factor from brew method – more a function of technique and recipe rather than the brewer itself.  This is mostly true – your brewing temperature is determined by the temperature of water you start with, and the thermal mass you achieve in your brewing liquor/slurry.  A pourover brew with the bed kept very, very low with a slower pour will have a lower brewing temp than a faster pour and a higher cone – presuming water starting at the same temperature.  This is often exaggerated further by a slow pour from a pouring kettle which is losing heat as well.

This isn’t to presume an ideal technique, just to highlight that the brewer doesn’t really control the temperature.  Except for one:  the syphon.  I find it odd that the temperature profile of this brewer isn’t discussed more.  It is rare to brew coffee in an environment where the temperature is held stable across a period of 1 to 4 minutes, as we usually do not add any energy beyond the brewing water to the brew.  Many people dislike the taste, or are simply disappointed by, the taste of coffee from a syphon.  Some might argue that this is because the person brewing lacks the particular ridiculous ninja stirring skills, but more likely the temperature profile of the brew is what is making it stand apart. 1  In terms of combining infusion and pressure driven percolation it is remarkably similar to an aeropress – something which rarely is discussed.

Speaking of stirring we can discuss agitation.  This is a topic that we are a little squeamish about as an industry, because we’ll almost instantly wheel out the words “inconsistent” or “unrepeatable”.  Usually this is in relation to the manual movement of the coffee with a tool – such as stirring the bloom of a pourover, or stirring the slurry of a syphon.  I’m skeptical of magical stirring techniques in any brew, and it feels like we should also be looking at the other agitation going on – when the water hits the coffee.  How we pour, where we pour, from how high we pour – all this and more will affect the movement of the coffee in the bed and more movement will result in more extraction.

Once again – this isn’t really a function of our chosen brew method – more our chosen technique.

So far there really hasn’t been much about the brewing process that is determined by the brewing device, rather than the brewing human.

Filtration

As we look to other attributes of the coffee an obvious place to see the impact of the brewer is the influence filtration medium.   One important aspect of coffee is how it feels to drink – the body, the mouthfeel, the texture.

This is determined by several things divided into two categories:  Dissolved things and Undissolved things.

The quantity of dissolved things determines our strength, the more solubles the stronger the drink will be and the heavier the body and mouthfeel will be.  This is linked the extraction (technique again) and recipe – not the brewer itself.  The coffee determines the composition of the solubles, and certain coffees contain solubles that increase our perception of mouthfeel.  All brew methods produce a cup where the dissolved solids play a fundamental role.

Undissolved solids are interesting too.  The undissolved we most often talk about are the lipids (oils) in the coffee, and also the tiny pieces of coffee that can be suspended in the brew.  These both have strong influences on the mouthfeel of the resulting coffee, not always in a beneficial way.

Paper filters are considered the most thorough way to remove the undissolved solids, resulting in a much clearer brew with an attribute we would often describe as clean.  Cloth filters allow through more of the undissolved materials, noticeably the lipid fraction but also some of the fines too.  However, there is usually so little fines overall that we usually experience a fuller mouthfeel – something most enjoy and I think cloth would be a more popular filtration method if it weren’t for the annoyances of maintaining the cloth and preventing it imparting unpleasant flavours.  This leaves metal filtration which simply removes the largest pieces of suspended material (i.e. the bulk of the brewing grounds) and results in a cloudier, muddier brew that can still be incredibly enjoyable even if that final mouthfeel is probably worth leaving in the cup.

So far, with the various factors discussed, it appears that the brewer has relatively little influence on cup quality compared to technique and few brewers demand certain techniques – instead allowing infinite varieties of recipes, methods of agitation, or brew temperatures to be used.  There is, however, one more distinguishing factor that should be discussed.

Infusion Vs Percolation

This is probably the biggest distinction between brewers, and the most important.  We have brewers that are solely infusion – like a french press – where extraction occurs as coffee infuses into the water.  We have percolation brewers where water flows through a bed of coffee, washing out soluble materials, and we have hybrid brewers where both occur at different stages – such as a syphon where the water a coffee steep, before the heat is removed and the water is dragged through the bed of coffee against the paper or cloth filter.

When it comes to assessing techniques and extraction I think it is fair to say that using infusion it is easier to achieve relatively uniform extraction, compared to percolation.  With percolation something is driving the movement of the water – it might be gravity, or applied pressure – but this means that paths of least resistance are preferable for the brewing water.  We must adapt techniques to allow for this, and help prevent too much uneven brewing.

Uneven brewing is a problem because it is so hard to measure – outside of taste.  I firmly believe that measuring overall extraction is incredibly useful and has many practical applications.  The critics of measurement have often cited our inability to measure evenness as a reason to not bother measuring at all.  This makes absolutely sense to me, but perhaps not hugely on topic. (Clarification:  AndyS points out that this is a horribly phrased, confusing sentence.  My explanation in the comments follows.)

The fact that extraction measurement can’t quantify evenness is not a reason to abandon and ignore a very useful tool that does exactly what it promises: to measure how much of the total coffee was extracted.  Pointing out what it can’t do as a flaw creates something of a straw man argument to me. Same thing as pointing out that it is misused and therefore a bad tool. (which I see online a lot too)

Creating a brew recipe

Have I argued that any brew method should be able to brew any coffee as desired, or have I argued the opposite?  To answer the question I thought I’d look at how I might make a choice about how I would want to present different coffees, and how I’d choose a brew method or recipe.

If I love a coffee because it has a plump, sweet fruit quality then I might choose to brew it using cloth filtration at a slightly higher recipe than usual.  Considering I take 60g/l as my own preferred starting point, I might instead brew at 65g/l to further emphasise the body.  When talking about the coffee I want to highlight a few simple reasons why someone would enjoy it, and then use my prep to make those points evident.  Plush, rich, heavy, jammy mouthfeel is a big promise, but I feel that if fulfilled a great experience would be had.

Conversely, if I loved the light, delicate tea-like quality of a floral coffee then I might drop back to 55g/l, and make sure it was paper filtered and brewed with a relatively hot brewing liquor.  Sometimes reducing concentration can help with clarity.  I’m not saying all coffees like this would be brewed this way, but to instead talk a bit about how we might think about our recipes and analyse our brewing choices.

I don’t think I’ve really come to any conclusion here, nor did I really mean to.  I just wanted the opportunity to write up a few thoughts on brewing and try and give them some structure.  I’m open to input on this, open to disagreement and probably being wrong about a whole heap of things.  On the one hand I feel like I’ve missed out a great deal but on the other hand this post is probably long enough!  I look forward to your feedback!

  1. My personal preference for coffees to brew in syphons would be very light roasted, dense coffees, that are often difficult to extract  ↩︎

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