30 Jun 2014

Tutorial: How to Cold Brew Coffee

80 grams | 1000mL | 60C+room temperature | 8hours-4days

An other subject for this post could be 'Why Cold Brew'. The opinions on cold brew as a brewing method vary dramatically. From it being 'velvety, sweet and without any sourness and bitternes' to it being 'flat, pale and completely uninspiring'. As Tim Wendelboe said to a bold barista serving him his cold brew Panama Geisha coffee: "No one has ever had a good cold brew coffee". At the same time renowned coffee companies such as Stumptown, and many others, are bottling and selling cold brew coffee very successfully.

Why the debate? Again, it is all about extraction and flavour. What the beverage coffee really is, in essence, is solubles extracted from the roasted and ground coffee beans into water. Now, if, how and when these solubles dissolve in water depend on a lot of things; roast, grind size, pressure, extraction time, of course the water used, and then also the temperature of the water. Hot water dissolves much more easily than cold water. Imagine your sugar dissolving into your hot tea (I said imagine, not do it. Please get a better tea product if you feel you need sugar in your tea), and then imagine dissolving it in a cold glass of water.

Why would you not brew a cold brew? Many people prefer making iced coffee over cold brew coffee. Iced coffee is when the coffee is brewed hot, but cooled quickly on ice to lock in all the volatile aromas and flavours that evaporate when brewed coffee cools off naturally. Usually the coffee is made using a pour over method, using only half the amount of hot water you would normally use. The other half of the water ratio can be found in ice blocks on which the brewed coffee lands. The positives of this method is that you keep the acidity in your cup of coffee, which is often lost in a cup of cold brew. According to Toddy, a cold brew method, 65% less of the acidic compounds end up in your brew when made with cold water compared to hot.
However, positives are that the mouthfeel of cold brew is very velvety, soft, sweet and balanced. Plus it often lacks acidity and bitterness, which can be a positive instead of a negative. Also, because it was brewed cold, the end result is very stable. Temperature differences change the flavour of your beverage. So when you brew your coffee hot, let it cool off, let it stand, or use it for cooking, the flavour you started with will be different to the flavour you end up with. The fact that cold brew was made with cold water means the flavour you get, you get. This makes it ideal to store (up to 10 days without flavour changes, if sealed and refrigerated) and to cook with.

Of course, during a hot summer day, it is also ideal to drink. Below my own cold brew recipe.

what will you need?

- 80 grams of coffee
- 1 litre of, preferably filtered, water at room temperature
- 1 bottle, glass or heat resistant plastic
- chemex and chemex filters (can be substituted with pitcher, cloth or felt filters)
- kettle and pouring kettle
- precision scale
- grinder
- time

- funnel

step 1
Weigh out the coffee. Really, step 1 is choosing your coffee, before weighing it out. I used a Guji Ethiopia coffee, light roasted by Czarny Deszcz out of Poland. The classically more acidic and fruity coffees, such as an Ethiopia, but also a Kenya, often result in a cold brew that is very light, sweet and fruity. These cold brews are best drank black or with a little cane sugar to bring out the fruity freshness. Of course they can also be mixed with milk, but watch your ratios.
When using a Central American or Indonesian bean, often the cold brew will have more body. Making them ideal to drink black or with milk if you so desire.

For either, choose a light to medium roast.

Now that you have the coffee you want to use, weigh it out. You will need at least 80 grams of coffee for one litre of water. Again, experiment here. Sometimes a little more than 80 will give you more depth and body.

step 2
Grind your coffee to medium coarseness. Aim for something that looks a little finer than caster sugar or sea salt.

step 3
Now warm some filtered water (double the amount of grams of weighed out coffee) up to 60 degrees Celsius. Put your ground coffee into a bottle you can close off. I used a glass bottle. But you can also use plastic, as long as it can take 60 degrees Celsius. If you are having some trouble with transferring your ground coffee to your bottle, grab a funnel.

step 4
I like blooming my coffee. Although we are using a submerging method, where all the coffee is submerged in the water, I believe the blooming still adds a positive flavour aspect to the end result. If you want to learn more about blooming, read my previous blog post.

To bloom the cold brew add your warmed water to the bottle slowly. Once you have added double the amount of grams of weighed out coffee in water, slowly swirl your bottle round to make sure all the ground coffee is wet.
Let this stand, while you get your filtered room temperature water.

step 5
Add your room temperature, preferably filtered, water to your bottle. Screw on the lid and agitate. In other words; shake it up, swirl on, tilt with vigour. Until you are sure your ground coffee and water are mixed well.

step 6
Leave your bottle in the refrigerator. The extra coldness while extracting will give a cleaner tasting cup. You will need to add a few more hours of extraction time to compensate. Usually your cold brew will need at least 12-24 hours to extract. When using a refrigerator, always lean more towards the 24 hours. And experiment with longer extraction times. The licorice flavour that some cold brews have, dissapears and the cold brew becomes much more clean, clear and sparkling with a longer extraction time. The most amazing one? An Ethiopian Kochere left for 4 days that tasted of clear watermelon juice and sweets. 

step 7
After waiting a day, get a thick filter, either thick paper, felt or cloth and strain your extraction, this will take a long time... You need some kind of substantial filter, to keep the fines out of the beverage. A regular paper filter thus, does not suffice. I used a chemex and a chemex filter. When using a thick paper filter, be sure to saturate the paper with water first, otherwise you can add paper flavour to your cold brew and that would be a real shame.

If you do not have a chemex, you can use a bottle or pitcher to catch the coffee into, use a cloth or felt filter and something to let this filter rest in. Be creative (if you are, send pictures).

step 8
Rinse the bottle you used to make the cold brew and pour the filtered extraction back into it. And presto, your done.
Keep your cold brew sealed in the refrigerator and it will keep for about 10 days without loss of flavour.

When you drink it, drink it cold. Either black, or with ice. You can add a little syrup to enhance the sweetness and acidity that is already there. Or you can drink it with a little milk. Or even try some alcoholic drinks, if that suits your fancy.

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