We love cold brew. We love how clean and crisp and refreshing it is. We love how complex the flavours can be. We love how the super-long extraction allows the true character of a coffee to shine through in all its gorgeousness. And we love how much you love it.
To that end we’ve spent most of this summer working to understand the process of cold brewing and perfecting that process. We’re not talking tips and recipes, we’re talking bottles of it, brewed to taste as exquisite as cold brew can, using specially-developed equipment under the exacting eyes of our expert coffee team.
And now we’ve cracked it. The production methods are small scale at the moment (there are only 48 orders available as we write) and the presentation is all a bit rough and ready. But a makeover can wait, because the quality of this cold brew speaks for itself.
Here’s how we did it.
First the technique.
Initially we experimented with V60s over ice but an overly bitter taste profile emerged as the hot coffee cooled. Conversely the longer extraction process of cold brewing produced a more balanced sweeter profile. The reason for the difference is the higher temperatures of V60 brewing are powerful enough to extract the bitter elements of the coffee from the ground, whereas a cold brew leaves them unextracted.
So, we began work on a cold total immersion method, using a large coffee filter within a sealed vat. Results were disappointing, tasting more like vaguely coffee-flavoured water than decent cold brew. So we tried a finer filter. There was some improvement but the team weren’t satisfied so we mixed the coffee directly into the water and allowed the extraction to take place over 24 hours, filtering it post-extraction.
Since coffee is essentially an emulsion of oil and water we used a nylon mesh filter to remove the grounds. This left behind the oils and fats that give coffee its enjoyably rich and heavy texture. The results tasted good but during feedback sessions with the team, the oily residue left behind by the nylon filter was found to be unpopular. We needed to filter it further.
Then modifications and problem solving.
The next logical step was a double filtration process, first with nylon and then with paper, similar to that we’d use with a V60. We found that as the oil was removed, the aromatic capacity of the coffee expanded. It tasted fantastic, with really nice clarity and excellent balance.
If this makes the production process sound simple, it shouldn’t. As we developed our cold brew other issues arose and modifications were made accordingly. Through various tasting sessions the team noticed oxidisation was creeping into the flavour profile, resulting in an unpleasant staleness. The vat needed to be made airtight to counter this, so the equipment went through one of many overhauls.
Pasteurisation was also no mean feat, but something we were committed to achieving. The solution – it turned out – was to manufacture what is essentially a 40 litre sous vide, which holds the coffee at an exact temperature for a sustained amount of time, allowing the flavour compounds to develop gradually.
Then the bean.
In the bid to find the perfect cold brew bean we tried every single coffee we stock. At the outset we anticipated a tried and tested favourite like Planalto would fare the best. This well-balanced chocolatey Brazilian has long been a favourite on the Pact menu, among customers and the team alike.
But in the process of trial, error and more trial we made a discovery. The coffees that are most perfectly balanced when brewed with hot water become unbalanced when brewed with cold. Planalto, when extracted through our cold brew process, didn’t have enough acidity to balance out the taste profile and its distinctive and popular characteristics were lost.
We soon discovered the opposite was true for one of our Ethiopian washed coffees. Brewed hot this coffee, Kayon Mountain Guji Washed, can have an intense acidity taste profile and a lingering bitterness which, while really popular with some customers, makes it a bit of an outlier on our menu. But when brewed cold Kayon Mountain Guji Washed came into its own in a way that staggered the team. Suddenly a slightly difficult, punchy coffee revealed a delightful acidity profile and a really unusual toffee sweetness that the team hadn’t really encountered from a coffee before, least of all an Ethiopian. We’d found our coffee.
So, what little we’ve managed to produce so far is ready for you to try. When Kayon Mountain Guji Washed is extracted with the cold water its harshest acidity remains unleashed, while the paper filter enables a release of volatile aromatic compounds that increases the complexity of its flavour profile. Put simply it’s cold brew at its best.
We’re immensely proud of it and we sincerely hope you enjoy drinking it as much as we’ve enjoyed perfecting it!