I’ve another post coming on why I blog, but this reason deserved a post in its own right.  A few days ago Shaun dropped me an e-mail about the Vinturi.  He’d played with it a little bit and thought it was interesting, and thought it might be something that would interest me. I admit I was curious – so I grabbed one from the UK website.  (Clicking through may help explain the image above!)

As I write this I confess I know very little about the science of aerating wine – feel free to point me in any link-based directions!  I didn’t know if it was specific to wine/alcoholic beverages with very volatile fractions, or whether it would affect coffee too.  I’m rather lucky in having Anette who is very good at tasting things – so I gave her several different brews split into pairs of cups, one aerated and one not.  Each time she said one cup tasted noticeably better, and it was the aerated one. As I was the one conducting the tests I’m rather biased, so feel free to discount this – but I thought the aerated cup was sweeter and had better clarity.

One obvious explanation would be that the aeration cooled the coffee, so comparatively it was the easier cup to taste – I should probably check how much temperature is lost (though I did preheat the Vinturi before doing it).  I am sure a slightly cooler brew would have an advantage, and a noticeable one at that, over the same hotter brew of the same coffee.  Simply pouring into a cooler cup could well create an advantage.  However the use of aeration in wine – which, again, I don’t understand yet – does intrigue me.

Yesterday we dropped some espresso through it, and it was interesting.  We then brewed an americano, skimmed it (for this is what crema skimming was truly made for) and then aerated it.  It was the best american I think I’ve ever had.¹ Perhaps I simply wanted it to be.

I am well aware you could pull the “Emperors New Clothes” card on this one – but I still think it warrants a little attention.  If people can come up with some experiments that will isolate the aeration then I’d be willing to try them and perhaps open the doors at work to people who want to take part in a little experiment too.

I will keep playing with it, and report back after a bit of reading on the science (if any) behind it all…

1. But I haven’t had that many, and I never really liked them to begin with!

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.

At the moment I still can’t give much away, it is nothing to do with espresso, it isn’t a coffee brewer either but I hope it will be great.  I have yet to see a finished unit, and I gather the aesthetic side is still quite open.  I’ll likely be heading over on the 1oth for a quick play with it, and to make coffee for people at the show and to talk about the project a little more.

Like a kid in a candy store…….

One big question was:  “Why break and then skim?  Why not just skim?”

This seemed like a pretty good question to me, so today I decided to do a few quick tests.

I took two identical presses, the same dose of coffee, the same brew water, temp and time and then after 4 minutes broke and cleaned one, and just cleaned the other.  I then tested out the TDS in each cup of coffee.

A TDS meter is useful, but limited.  It will tell you how much is dissolved in the water and nothing more.  Here I wanted to see if one cup was stronger than the other.  It turns out one was – and by quite a significant percentage.¹

The broken and stirred cup was stronger, usually by around 0.2%.  This doesn’t sound like much but when you do the maths backwards you find that it is a swing of about 3% of the ground coffee solubles extracted into the cup.

I want to do some more tests on this, and I want to do some blind cupping of it as well.  However it would seem that if your grinder produces a lot of fines, and when making press coffee it seems to easily overextract then I would just skim, opposed to breaking and skimming.  It could be that a different dose and steep time could yield better results.  I am waiting for Mark Prince’s article on his press technique because I know that while he skims but doesn’t break he does use different parameters.  It may be that one style might highlight a certain coffee better than another, who knows – I am just interesting in learning more about all this.

1. It should be noted that I haven’t done this experiment enough times for it to be seriously useful – if anyone out there with a TDS meter wants to contribute then please do!

The first thing that upset me was just how hard London’s water is. Out of the tap I get 410ppm, which is pretty hard. This means it is not ideal for brewing coffee as it is less “hungry” for new solubles than softer water. I didn’t realise until I started testing just how badly it was affecting the coffee.

Testing some of Tim’s coffee brewed on the skinny Chemex

I was struggling to get into the Golden Cup zone of 18-22% extraction which, through years of filter brewing, is considered a suitable target. Different countries might like different strengths of coffee but they all generally like 18-22% of whatever dose that is.

I have know switched to bottled water for brewing (with a much more attractive TDS of 130ppm) and the coffee does indeed taste much better and my extraction percentages are up even though I haven’t changed the grind or dose. I had gotten used to a very coarse grind on the Chemex (after being advised by Kyle in Intelli.la) but have slowly been bringing it finer to get the percentage up. I will keep doing more but wonder how many other people out there have TDS meters and whether they have compared their brewers with different grinds and doses and compared the cups after.

To this end I’ve done a little spreadsheet that negates the need for a brewing chart as the maths is built in. It works on 2ml of water being absorbed by each gram of coffee but you can change that too. Input the amount of coffee you use, the amount of water you brew with and then TDS measurements. I’ve left columns in there for other useful data – such as brewer, coffee used and notes on grind settings. I probably should have found a way to include a cupping score/notes but haven’t. If anyone else fancies having a go then do download it and let me know how you get on. Once I have enough data I will post up about my Chemex experiments.

Thoughts and comments welcome….

TDS Testing Spreadsheet


downloads

UPDATE
Mike Khan from Bunn sent me his spreadsheet which does percentages and graphs for each brew you do.
Mike’s TDS Calculator


downloads





Thank you Mike!

The spread of the Clover

I am hoping this year sees people less obsessed with it as new technology and start to treat as a standard brewing device moving emphasis away from the machine back to the coffee. I could be really brave and predict that Starbucks will start using them, but I think the guys at Clover would curse me for jinxing them! I also predict I’ll buy a couple this year, but I am fairly sure that will come true…..

Clover puck

World Barista Championships

I am not going to be as bold/stupid as to try and pick a winner but I think the shift away from a Scandinavian-heavy final will continue. I am not saying that none of the Scandinavian countries will be there, or that a Scandinavian won’t win, just that the rest of the world has caught up (in competition terms) and that it really is incredible open. I can’t wait to see the performances in Copenhagen!

Coffee prices continue to rise

Whilst I am aware that Speciality pricing doesn’t have an absolute relationship to C-market pricing, but I think a lot of factors will help drive up pricing. Those of you who keep an eye on the coffee news feeds will see a lot of stories about reduced production in a lot of countries, plus the increasing demand for high quality coffees is (I’d guess) rising slightly faster than production is which will also push up pricing. I suppose, as someone about to start buying green, I ought to wish prices would stay low but I love the idea of what increasing spends could do for quality of the ripe cherries picked and the greens produced.

Pressure profiling in espresso

I know this isn’t a new idea, but I think 2008 and could be the year people are willing to experiment more with it and equipment mods/hacks get easier to implement. The open source nature of the internet could help contribute to a faster “dialling in” of profiles as people share their experimentation. I think that improvements could well be made outside of a flat line profile and if anyone wants to point me in the direction of how to install some sort of pressure profiling device onto my GS3 I’d be very grateful, or tell me if I should just do it on a one group Cyncra.

The continued rise of the micro-lot

Hopefully the term and the concept will spread further and further. I love the idea of one or two dozen bags of something special, something fleeting and interesting for consumers and another way to inject more money into farm level. Highlighting both seasonality as well as varietal, terroir and processing I think they are a great bridge to customer interaction.

Plus I need something different and tasty to drink from my growing range of mugs (which I hope become as collectible as espresso cups!)

A cup of Tim Wendelboe’s Guatemalan microlot

So – what are everyone else’s coffee predictions? Leave a comment, post a reply on your own blog – what do you see changing? What do you want to change? New products? New ideas?

However I was thinking about brewing stale coffee as espresso, and then thinking about measuring filter brewed coffee and an idea cropped up.

To me, when I brew stale coffee as espresso it seems that there are a lot less solubles in the brew – the pour looks very pale very quickly, if not all the way through the shot. So based on this observation I propose an experiment using filter coffee.

Roast up 5 kilos of a coffee and then set up to brew as filter coffee so that the percentage of extraction is around 20% for the chosen weight of coffee. (The brewing charts may differ on ideal strength but they all agree that 18-22% of solids extracted is considered ideal.) Let’s say we use a Nordic dose of 70g per litre.

Once this grind has been set for that dose then 3 brews a day are done for that recipe with a fixed grind (the grinder kept cool – no back to back grindings). The resulting brews are then measured for TDS, as well as the brew water so an accurate log of extraction percentages could be kept. This daily experiment is then repeated for 30 days and the results graphically logged.

The coffee could be kept a number of different ways for each type of experiment – craft packaged, valve packed, valve packed and nitrogen flushed.

I would hypothesize that though everything was kept constant (grind/dose/brew temp and volume) as the coffee aged it would start to be more difficult to extract. Whether you chose to see the point at which the coffee drops below 18% as the point it is stale, or perhaps another point that has some repeated statistical significance I don’t know. However I think that one could likely find enough data to give a reasonably accurate shelf life for truly fresh coffee.

It would also be interesting to couple the metering tests with cupping, but I worry that it would be too difficult to be objective/difficult to set up well.

I am sure this has flaws and would welcome any input on this before I start to play with it. (Plus I need a TDS meter!)

Thoughts in the comments please?

After some comments in the thread about using scales to brew my Chemex on brew temperature I decided to perform a few rounds of experiments. Simple really, I just placed a probe (K-type, not ideal but it will do) into the bed of coffee, poured over the water and waited to see what would happen. The first test gae me an unexpected result.

Brew temperature of a Chemex

What I expected was a steady decline in temperature during the extraction, and over a couple of minutes losing a fair few degrees, due to the area of steeping coffee being quite large. When the probe was in at the top of the brew the total heat loss was about 2C. Not much at all. What was interesting also was the temperature gradient throughout the liquid. At the start it was a couple of degrees from the top of the brew to the point of the filter cone and over brewing that stretched out to about 4 or 5C.

I’ve only done this experiment a few times so if you have the kit and a few extra minutes to spare I’d love to see it replicated – the coffee coming out isn’t much affected by the probe so it isn’t a wasted cup in the morning.

To completely and utterly hypothesize – it seems the floating crust of grounds does wonders for insulation, possibly with the help of CO2. In the next round I’d be tempted to stir and skim like a cupping bowl to see if this accelerates the cooling.

Thoughts anyone?