So, summer is right around the corner, and when the temperatures start to climb and the sun is out, there's no better way in my opinon to keep cool than with a delicious glass of Cold Brew Coffee.
Cold brew is something that you can buy bottled from some coffee shops, or in this blog we're going to talk about making it yourself with this super easy, but very delicious method using the Hario Mizudashi Cold Brew Pot.
The Science of Cold-Brew! (Skip if you just want delicious coffee!)
Cold brew is a different method of extraction to how we would normally brew coffee, when brewing coffee we're aiming to extract soluble material from the ground coffee into water, and the percentage of TDS (Total disolved solids) in the drink/liquid at the end of the brew is how we measure our extraction scientificly, but in flavour is also a huge indication of how extracted a coffee is. We grind coffee to increase/expose more surface area of coffee contact to water, which allows more of the soluble material to be extracted.
Heat effects the solubility of coffee, it aids in the extraction of soluble material and the oils in coffee into the brew water, which allows us to brew cups of Filter coffee in just a few minutes, and Espresso in around 30 seconds (With the combination of pressure in a portafilter) The heat element also increases the aromatic elements of coffee, through hot water extraction we get evaporation, steam, which increases the aromatics of coffee, giving that delicious 'freshly brewed coffee' smell we all know and love, but also increases oxidation of the oils and acids in coffee, increasing the sourness and bitterness of a brew- Try brewing a V60, taste it hot...and then let it cool and taste again. They taste compeltely different, and thats because as the hot water cools, oxidation in the brew happens which causes the flavours to distinctively change, sometimes for the better...(Some coffee's actually grow sweeter as they cool) some times for worse.
Cold water extractions react differently with coffee, the combination of cold water and coffee means the extraction takes much longer, there isnt heat applied to the ground coffee to help guide the Soluble material out the coffee, so how do we achieve good extraction without heat?...Time.
Cold Brew extractions take much longer, where as a V60 extraction we would allow around 3-4 minutes, for a Cold Brew extraction we're talking anywhere from 4...to 24 hours for an extraction, which might seem like a drastic increase, but we're trying to achieve a good balance between great extraction, and limited oxidation. Cold Brew can last in your fridge anywhere up to 2 weeks! So giving it around a day to extract isn't so much to ask in comparrison.
So to begin with, this brew focuses entirely around the Hario Mizudashi Cold Brew Pot - The pot we're brewing in today is a 600ml cold brew capacity, they also do a 1ltr version.
We love this brewer because its simple, easy to clean, very little mess and durable - The Glass is Borosilicate glass which makes it much more stable for temperature fluctuations to prevent cracks and breakages, and its dishwasher safe which is always a bonus!
For our Coffee again we're going with a filter favourite, our Colombia Inza Region 1, this is a deliciously fruity, tea like coffee which lends its qualities greatly towards a Cold Brew method, resulting in a full bodied but sweet brew, perfect straight...or with milk over ice.
Brew Ratio- With Cold Brew extractions, I would recommend that what ever brew ratio you're used to working too... add an additional 5 Grams to your coffee, the additional coffee helps massively with the balance of flavour, cold brew is something you can always dilute down with fresh cold water afterwards, so if your brew is a little too strong for you, Just add a little water until you reach a strength you're happy with.
For the 600ml Brewer, we're using 40Grams of coffee, to 600Grams of water, a 1:15 Brew ratio.
Grind - Now for this length of extraction, we don't want to risk over extracting the coffee which could ruin the brew, instead we want a course grind to allow that slow stable extraction, with not too many fines which could turn the brew bitter or astringent.
For this we're using a Wilfa Home Grinder on the Steap setting, on the courser end of french press level grind, to achieve the following Grind size.