Prufrocker: The Blog

The Single-shot Cartel

Strength, price and the perfect coffee.

by  |   |  Coffee Science


I can double the efficiency of your staff and save you 36% on your coffee bill right now and probably no one will complain. But you need to agree to use 36% less coffee. And you need to agree to use 76% more water. I can throw in improved life expectancy of your grinder (theoretically), and I guarantee the coffee will have better crema, be less sour and Jay Rayner will possibly, (though I offer no guarantees here) possibly like it. Now some napkin maths and some extraction stuff.

Hypothetical cafe order #1: A double espresso
Naked portafilter
18g dose,
34g beverage weight.
TDS (Total dissolved solid) 8.0%
Prep time 45 seconds.
Extraction yield 17.1%

Order #2: Two Single Espressos
Spouted portafilter
23g dose
30gx2 beverage weight.
TDS 8.0%.
Prep time 45 seconds.
Extraction yield 21.5%

I am producing single shots in the London Barista Resource that are the same volume as our doubles when we opened our doors in 2009. They are only 12% smaller than our existing doubles. I am using 27% more grounds but am producing two coffees simultaneously that I enjoy more than what our baristas are producing upstairs.

Our best double shots with 17.5g doses and 34g beverage weights might reach 9.7% TDS, which just crests 19% extraction. These will receive high scores in our espresso  journal. But I’ve recently become  a bit more of an 8% man and am looking for higher scores and some more drinkable drinks. I’ll not claim all the credit for this two-coffees-at-a-time idea. It has considerable historical precedent. You could in fact make three coffees at once with these bad boys.

Strength in the cup is measured as TDS (Total dissolved solids). The TDS of red wine is about 5%. Filter coffee is usually between 1 and 2%. The TDS of London water is 0.03%. We know you can make a coffee stronger by using more coffee. We know you can do the same by extracting more. We also know it is almost impossible to over extract light roasted coffee when using an 18-34g. The tendency is to under-extract and to fight this we get better grinders, titanium burrs, Pergtamps, IMS shower screens and VST baskets and we grind finer so that we might creep into the 19% extraction yield range.

The recent tendency of speciality coffee shops has been to reduce doses which should help improve the water’s ability to extract coffee. This down-dosing has perhaps been at the expense of aroma. When we opened Prufrock, we were at 19g and were producing 30g doubles. We have wound it back to 17.5g producing 34g to combat under-extraction. It’s reaching the point like in a game of snap, where we can pile the cards back up, split the pack and start again. But the machines and baskets at the moment aren’t designed for massive doses.

I can’t really get any bigger than a 30g single and produce a shot that can stand up to the required flavour intensity and body requirements of Prufrock Baristas. The biggest basket I can get my hands on at the moment is a 22g VST. If I had an even bigger basket I could probably get 34g beverage weight in each single shot at 8%TDS. 2mm more depth to play with wouldn’t hurt. I may also get better extraction if the baskets were wider. Might have to wait a while for that innovation. Stop press. Gwilym Davies and Klaus Thomsen via twitter just sent through a correction to that last statement. http://flic.kr/p/2ARMga

The general consensus among our baristas is that these long shots are no worse and no better than what we are currently producing for taste balance and texture. But for Crema scores, I am running a score sheet demolition. Loads of coffee, loads of water and a fast flow is the stuff of ample crema. It vexes me that we produce such poor crema these days with light espresso roasts, rested beans and 17g singles. Even the most au fait customer still uses crema as a barometer of freshness and good extraction. These 23g-60g split doubles have plenty.

To measure TDS in a cafe you need to get a refractometer and they cost plenty of money so when we teach, we emphasise the role of scoring as the main criteria for designing recipes. As a UKBC and (Czech) CBC judge and having had the invaluable opportunity of calibrating with world judges, I’m feeling pretty sure that an 85point blend will hit a ceiling of 4 out of 6 for Crema, Taste balance, Flavour and Tactile on the WBC score sheet.  In our espresso journal we are happy if we can get 4s with an 85: Very Goods but not Excellents.

I have been using 23-60g recipes for split shots at the BRAT over the last month and am getting 4s with 85point coffees. Sometimes with an older coffee  in the blend they can taste a bit papery but are also always easier to drink. Why are they easier, to drink? Because they are always sweeter and a bit more watery than their 17.5-34g equivalents. My lowest extraction yield to date has been 19.5%. At this brew formula it is almost always about 21%. Gwilym is quite focused on optimum extraction levels for individual coffees. This takes a huge amount of testing, but what Prufrock is trying to achieve with this pilot is being able to move around the gold box with our espressos rather than just squeezing everything we can get out of them whilst remembering to turn the button off at 34g. I want elbow room above 19% and no technology that I can see is going to give it to us right now above a 50% brew-formula.

Sang Ho Park, roaster at Square Mile and UK brewers Cup Champion stated at the Prufrock Brewbar last week he is enjoying 8% shots. James Lowe at Lyle’s on Bethnal Green Road over the bar tells us he’s at 17g and was serving wonderful shots of very light roasted Koppi which I would very much imagine were in the 8% range. They were EK shots and a good 50g. I would guess the Bulldog edition is at 8-9% in general. It gets me thinking that the EK has taken all too much credit for increased extraction yields and the real unsung hero of improved flavour and sweetness in modern espresso is the old fisherman’s daughter-water. Even Andrea Illy I might suggest is an 8% TDS man. Take 14g as he stipulates, produce a 50ml extraction (which I’m guessing would weigh about 36g) at 20% extraction you’re on 8% in the cup.

All this up-yielding must come with a disclaimer. The saving is only beneficial if there are two customers around to serve simultaneously. It is in fact not the best idea for your guest coffee which might only be ordered once in every 10 customers. This blog post goes out to the volume grinder, the milk blend, the people’s choice. This concept comes hand in hand with the necessity of switching out a double and bringing in a single basket for single serves. (At least this will provide a forum for any redundant naked portafilters. If there is only one customer around, and your brewing on this kind of recipe, you could find yourself suddenly spending 27% more on your coffee bill and be guilty of committing that most archival of barista offences; sending half the espresso into the drip tray. In recent years, single baskets have enjoyed a design renaissance which we have not been participating in properly but will now be embracing with open hearts. Our last research of single baskets occurred before these wonders existed.

This new recipe presents a few opportunities. We could put the price of our coffee down. Or…it is a chance to spend 36% more on our coffee. So to celebrate this I have gone straight to the nearest source of Hacienda Esmeralda I can think of, lovely Coffee Collective in Copenhagen and we will serve some Gesha on espresso during a pilot stage of this experiment and see what the customer reception is. I should point out this coffee is about 6 times more expensive than our usual offerings to buy in but the idea stays true. With an alteration in brew formula and at no extra cost, we can put ourselves in a position to serve coffee that is a good 5 points out of 100 higher with twice the efficiency. So we can probably get those 4s up to 5s or more whilst giving our baristas an easier life. With lower brew formulas comes improvements in ingredient quality at Prufrock and a good deal more elbow room.


/