Posts Tagged ‘filter coffee’

An experiment to determine freshness

Friday, November 23rd, 2007

Freshness is one of those difficult terms in coffee because it is often considered quite subjective.

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?

SCAE Brewmaster Certification

Thursday, November 8th, 2007

In the world of Speciality Coffee filter coffee isn’t very sexy. One criticism leveled at the SCAE is that it seems obsessed with espresso and yet espresso only makes up a small percentage of how all coffee is consumed in member countries so they have started a Brewmasters program.

Anette and I traveled up for a two day course held at Bunn’s UK office to take part. The first day is primarily lectures – Mick Wheeler gave a seed to cup, Christian Klatt from Mahlkoenig talked about grinding, and Shane Pender from Marco talked about grind size analysis. I’ve attended a fair few seed to cup lectures but there were a fair few interesting nuggets in there I hadn’t heard before and also another view point on the economics of farming. Equallly in a world with very little information on grinding coffee it is always nice to be able to ask difficult questions.

TDS Meter

Then it was onto the brewing lectures given jointly by Paul Stack of Marco and Mike Khan of Bunn. This was similar to the lecture given on filter brewing at the ETCC in Moscow, except in greater depth. Beyond better understand of the kit the focus was around the brewing control chart.

Brewing Control Chart

I am not going to explain it in great detail but essential filter brewing is a balance of extraction and strength – the amount of solubles taken from the ground coffee vs their concentration in the final brew. Extraction is hard to measure easily so with the chart you can test the strength and then, if you know your weight of coffee used, work back to the strength. The SCAE gold cup standard says that you should extract between 18-22% of the ground coffee, and that the final strength is between 1.2-1.45%. Interestingly there are other standards – SCAA, SCAJ or NCA and they all agree on the extraction but not on the strenth. Norwegians like a much stronger brew than the Americans – but everyone likes it properly brewed.

This all makes more sense on the course, I assure you. The first day ended with a written exam covering all the lectures.

TDS meter and control chart

The second day had a more practical focus. First Anette gave a cupping workshop, which is always a lot of fun and it was interesting to see how widely people’s taste preferences differ (I still can’t deal with the Malabar!). After this testing protocols were explained because the long view of this course is that we Brewmasters (I do love the title) are now able to certify a coffee shops filter coffee as achieving an SCAE Gold Cup standard. This is then verified by the SCAE by sending them a sample of brew water and brewed coffee along with details of the weight used to brew. (If you don’t send the water then they can’t subtract the solubles already in it, to give you an accurate reading of the coffee concentration.)

We all had to brew Gold Cup standard coffee, document it and measure the brew time and pH in order to pass the course. Which we all thankfully did – we were the only people not from a filter machine company, the rest were from Bunn, Marco, Animo and Bravilor.

Attendees at the Brew Master Course
I know the debate about what Speciality Coffee is will continue, but is nice to be able to at least measure good practise and standards and though good brewing doesn’t turn bad coffee into good coffee, it is at least tasting as good as it can. It is a great course, and I would recommend it to anyone – I guess it mostly has roasters in mind, or other coffee suppliers as they would be the ones verifying accounts. If you are curious then get in touch with the SCAE.  If you are in the UK I think they will be running this course at Hotelympia in February and if you are interested then drop Steve Penk and e-mail (sgp at laspaziale dot co dot uk)