It seems a lot of baristas, roasters and others in speciality coffee are looking to do research too. I’m posting this to ask where they are looking and how they are going about it.

Most don’t have access to published papers, and there isn’t a great deal of stuff online – everyone finds coffeeresearch.org pretty quickly but I think coffee has probably moved faster than that particular website has. ASIC is certainly a valuable resource, but perhaps inaccessible to those without a science background.

In their hunt for knowledge, I’m wondering how many people have grabbed the literature review published by the GCQRI, or have grabbed any of the resources on their site. What are people looking for? Bearing in mind there are no easy answers – are we just talking about wanting to do more research, and learn more about coffee rather than having a specific plan of action or a goal to our learning?

In the future there will be more information to share, mostly from the GCQRI, and I think it would be beneficial to understand how people do their research (honestly), to make sure information ends up in the right place. I’m not trying to catch people out here, I certainly spent a long time putting phrases into google and hopefully hunting through the mixture of garbage and occasional information nuggets it produced. I didn’t know a better way.

What about you?

There are two upcoming events and you’ll want to make it to both if you can:

6.30pm Friday 8th July – Multimodal Flavour Perception
Venue: Senate House, Malet Street, WC1

Charles Spence and Barry C Smith will explore the neuroscience and philosophy of tasting with some practical demonstrations, and explore the role the brain plays in the pleasures of eating.

How can you not want to come to this? More info here. Tickets available here.

7pm Wednesday 13th July – The Miraculous Egg
Venue: Westminster Kingsway College, Vincent Square, SW1P

Some of you who might be aware of the weekly egg consumption at the SQM HQ, and will find no surprise in how excited I am about this one. For those raising a concerned/curious eyebrow – the egg is incredibly fascinating (and delicious) to me. The range of recipes that use it – the range of textures of which it is capable – are astonishing. This will be very interesting.

More details here (scroll down), and tickets available here. Hope to see some familiar faces there this week.

I’m sure it is no leap to see where I am going with this, and also clear that I am not claiming this as original thinking!

I began to wonder if pressurised brewing could be applicable to more than espresso. Cold brewing (not icing hot coffee to dilute, but brewing with ambient/cool/cold water) is often a little disappointing. While you can get a balanced and tasty brew you sometimes miss out on some of the interesting aromatics and flavours, as well as the acidity, of some coffees – due to a lack of heat/energy to extract them.

Could pressure add the necessary energy – perhaps even allow rapid cold brewing?  I loaded a syphon with 15g of coffee and 250ml of water, pressurised it, shook vigorously and then waited a minute and released the pressure.  I strained it through a V60 and tasted it.  Disgusting, barely any extraction.

“More time….” I thought – so I set up a longer brew.  The results were very tasty.  I needed a control sample, so last night I experimented again.

The two brewers

I would use the same amount of coffee, water and use the same brew time.  One brew would be in a french press, left to steep.  The other would be pressurised.

Matching doses within 0.1g

For the coffee I used a test batch of the washed lot from Finca Killimanjaro, from Aida in El Salvador.  We’d already cupped it and I knew it to be juicy, tasty and not an obvious coffee to (traditionally) cold brew.

There is a lot less bloom with cold water.

I steeped them for 12 hours – the french press lidded and two charges into the cream whipper.  (If anyone knows how to calculate how much pressure the liquid was under I’d be very grateful!)

This morning I strained the two coffees in preparation for serving to the rest of the team at the roastery.  The french press brew looked fairly normal:

Straining the press pot

Straining the pressurised liquid was very different.  Overnight the gas had gone into solution and releasing the pressure meant that it began to bubble and fizz out (this is important – more on this later!).  It doesn’t look very appealing to pour a mass of fizzing coffee slurry into a V60!

Fizzing coffee slurry

The coffee also looks a little odd initially as I think it was still giving up a little of the dissolved gas.  Very quickly it just looked like paper filter coffee again.

Pressurised cold brew coffee

I served the two coffees blind to everyone, though it was clear there was an obvious winner.  Everyone picked the pressurised brew as being more delicious.  I checked the extractions with the Mojo and the preference made sense.  The ambient pressure cold brew struck out at a lowly 14% extraction.  The pressurised brew (with identical time, brew temp and grind size) came out at 18%.  This was a pretty significant change to the brewing process.

Now – I know what you are thinking:  Is the pressure speeding up the extraction.  My initial thoughts are:  probably not.

I think that the aggressive fizzing upon depressurisation and during the pouring process was effectively and noticeably agitating the coffee grounds increasing the extraction.

What I’d like to try next is to compare an ambient cold brew that gets up to 18-19% extraction (into the zone of deliciousness) to a pressurised brew of equal extraction.  I’ll probably need to agitate the coffee in the ambient brew to get it to do that without introducing a new variable between them of brew time.  This should also give a slightly clearer impression of the role of pressure outside of its agitating effect.

The coffee:  pretty damned tasty – and some nice acidity/juiciness in the cup which makes me hopeful.  We did it with one of the Kenyas we have (the Tegu AA lot) and it was seriously delicious.  If any of you have a cream whipper and some spare time and want to experiment too I’d love to hear about it.  Thoughts, suggestions and gentle berating for silly experiments always welcome in the comments!

I am not particularly ashamed of the phrase “I don’t know” but there comes a point in the day when you’ve said it five or six times and you feel you really ought to do something about it.

The cause of my embarrassed ignorance:  the change in flavour when coffee cools.

The change in a coffee as it cools is familiar to anyone, especially those who’ve cupped a lot.  I think I might have made the rookie error of associating the change with the cupping process too much – the continued extraction, the constant slight agitation of spoons.  I hadn’t really thought much more about it until customers at Penny University started asking and I realised the change was independent of brew method, filtration type (metal, cloth or paper) and common to all coffees.  Clearly something else is going on here.

I understand a few things about how temperature affects taste – the classic example being Coca-Cola.  Cold Coke is (shamefully) delicious.  Warm Coke is too sweet.  The amount of sugar hasn’t changed, merely our tongues capacity to detect it.  Though with coffee it clearly isn’t simple sugars, and one also experiences changes in taste, flavour and mouthfeel.

Perhaps there is something in the books that I own and I may have missed it, or maybe there are some good archived discussions online I haven’t seen.  It just seems like this is something important in coffee that we all talk about, enjoy and appreciate but don’t really understand.

Links, insight, indepth technical explanations, invitations to seminars in exotic locations and casual abuse for my ignorance all welcome!

Before I type cheese too many times I want to let people know that the next London Gastronomy Seminar is coming up and I am really quite excited about it.  There are more details here.

On a side note – Neal’s Yard Dairy are a company that I have a huge amount of respect for, not just because of the quality of their product but because they do such a great job of communicating it in their shop, and ultimately they are incredibly good at selling it.

There is lots to be learned here.  I hope to see you there!

The idea behind the seminars is to explore and enjoy the science of food.  Some people find that science, that understanding, can take the joy out of things but I for one find beauty and fascination in unweaving the rainbow.  I don’t think any of food’s delight and enjoyment is lost if we understand the mechanics of our recipes better.  Especially if, through that understanding, we can improve the recipe!

Having heard both Tony and John speak at our first forum I really look forward to seeing them present again.  (I also really need to get to Tony’s bar  - 69 Colbrooke Row.

I will probably post more about this soon, I am somewhat wrecked after a week of rebuilding the roastery and building out a new training room (and, you know, running a roastery!)

For those of you in London or nearby, I hope to see you there!

I might upload the presentation slides I used with notes at some point, but a little of what I spoke about is covered in a separate, and coincidentally written post on my other site here.

This first event was a precursor to a larger, public event that is planned.  I will post more details as soon as I have them, but if you are in London and interested in food and food science then it will be right up your street!

Brew recipes have been on my mind again recently, so I thought I’d post up this quick poll.  I’d love if it people could give me some data on this.  If enough people respond then I will post up the results, and any trends that occur.

A few quick things.  Please dial your espresso in to the point that you are happy.  It doesn’t need to be godshot territory, but something you’d serve to a customer or friend who you liked.

Secondly – please weigh things properly.  A lot of people speculate the weight of ground coffee they use, and very few people are accurate with it.  The more accurate the measurement the better.

Just to emphasize this because it is important – I need the weight of your shot not the volume.

Once you’ve weighed the shot feel free to drink it, to make sure it tasted good.

Here’s the poll:

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Maier (1985)¹  compared the chemical composition of traditional and fast roasted coffees, using samples of similar roast colour, and found that the water-soluble extract (soluble solids) increased as the roasting time decreased.  The content of specific substances (such as saccharose) changed with the roasting, indicating that chemical compositions of traditional and fast roasted coffee are similar but not identical.  As expected, fine grind of coffee samples led to an increased amount of extract.  Interestingly the difference in the soluble yield between traditional and fast roasted coffee was dimished by fine grinding. This supports the thesis that fast roasted coffee shows increased brew strength due to structural but not chemical changes.

I hope to have some time this weekend to look at a few more things, I just wanted to keep the debate going.  There is some more info on bean swelling that I want to post up too.

1. Maier, H.G. (1985) Zur Zusammensetzung kurzzeitgerosteter Kaffees. Lebensmittelchem. Gerichtl. Chem., 39, 25-9

As always the paricipants there were way smarter than me and offered several interesting options. I dropped into the thread that this was part of my idea of a grand unified theory of espresso, and subsequently a few people mailed and pm’d me asking what on earth I was talking about and what density had to do with it.

Well, I should probably explain what I have been thinking. ²

When approaching a coffee and brewing it using an espresso machine you are often searching for an ‘ideal’ recipe for that coffee.  For many of us knowing as much about that coffee as possible often helps make intuitive judgements about things like dose and brew temp.  If I get my science wrong then please, please shoot me down. ³

One of the things that broke my head about roasting early on was the discovery that the longer/darker you roast the less potential solubles you have.  This may seem obvious to some but it always felt like the roasting process created many new flavours but one must distinguish between flavours and solubles.  This explains why instant coffee is roasting very fast and relatively light – they are interested in a percentage yield so the more solubles the better, regardless of taste.

Knowing this then made something I had experienced make apparent sense – darker roasts generally prefer higher doses, because you need more coffee to get more solubles to get a nice, thick and pleasant espresso.  But after a moments thought it didn’t make sense.  This would mean that you would get a thicker, heavier cup with a higher TDS measurement from lighter roasts but lighter roasts generally produced delicious but lighter bodied cups.  What nudged me towards density was how we approach very high grown coffees versus lower grown coffees.

Higher grown coffees (and let me make a broad sweeping generalisation here) have a much higher acidity than their lower grown brethren.  When brewed as espresso they can easily yield extremely acidic and unbalanced cups and, taking unbalanced and pronounced acidity as a sign of underextraction, I found that higher brewing temperatures helped to produce a more balanced cup.

What do lighter roasts and high grown coffees have in common:  higher densities.  Though there was more to extract (in theory) you had to work a lot harder to do it.  Therefore reducing the dose of a lighter roast/higher grown coffee gave you a higher ratio of water/energy to coffee to help extract a tasty cup.  (I often think of heat energy as some sort of currency, with which you can buy solubles.  The more heat, the more you extract/purchase.)

This is all well and good for convenient examples – high grown, light roasts versus low grown darker roasts.  Give me a clean prepped coffee from relatively low altitudes in Brasil, roast it into 2nd and I will likely be dosing quite high and not brewing too hot.  I’ll certainly be dosing it very different from how I might brew a lot of Aricha as a straight shot.

But what about a light roast of a low grown coffee, or a dark roast of something grown super high up?  This is what lead me to wanting to find a way to measure and compare the densities of coffee beans to see if there was correlation between the density of the end product and an ideal brew temperture of particularly effective dose.

So – if I have had such a good idea why don’t I do all the research and then publish it all at the end of it and try and stamp it “Hoffmann’s theory” or something equally absurd? (Apart from the fact that it is absurd).  Because I want to generate a little discussion about this.  I want people to weigh in and tell me I am being stupid/simplistic and to suggest better ways to test these ideas.  I want to understand espresso better so I can make better tasting drinks and translate coffee’s journey more transparently in the cup. ⁴

I really hope people will offer their opinions on this idea, shoot it down or take it and run with it.  I am going to start doing some basic testing and see what happens.  Lots of little experiments appeal. ⁵

1. There really is no better place on the web for these kinds of questions!
2. Some of this is based on personal preference, some on what seems to be fairly well agreed upon within the community of people who worry a lot about their espresso.
3. There is another post in the works about the value of being wrong and discussing it afterwards – yes, I have a big wrongness to confess to…..
4. I know this is a wordy post and all, and I would have put some nice photos in but my camera is dead
5. For example – if I roast two coffees til their densities match – will they grind the same, and at the same dose will they extract the same?  Would they be ideal, therefore, to blend together to get the most out of each of them.  This probably shouldn’t be a footnote, but it is.  So there.