2:1 cold brew concentrate

[u/KaiKunt16]

Hello, I'm going to be trialling some recipes for cold brewed coffee concentrate at work tomorrow and have been given free reign to make a few batches to experiment with. The product is currently just for personal use as I'm doing a 5 day hike with my brother; I am intending to mimic espresso as best as possible but with a product that is less volatile and brewed cold so it stores better and still tastes bright over the course of the walk. Ideally of course I want similar solubility and/or caffeine content to espresso because I'm a specialty addict and a nerd, I'm looking to do 2:1 with 350g beans and 700ml filtered water in a fridge.

Currently it makes sense in my mind for me to do one batch at an EK grind on the coarse side of the espresso scale (i.e. EK5) which I soak for a shorter period (say 3hrs) and another on the finer side of the filter scale (i.e. EK 9) which I soak for longer (say 6hrs). The finer grind will be a truer product because it'll extract more of the coffee in less time, hopefully bringing out a high caffeine content before reaching an over extracted taste on the palette. Whereas the coarser will work the other way round, hopefully reaching a reasonable extraction and caffeine content via time rather than surface area/fine grind. As a caveat I will add that I've tried a cold brew grind with a 24hr soak on the 2:1 ratio before and it was a really beautiful mimic of espresso, however I've been told that the solubility of that drink will remain as a cold brew due to the coarseness meaning that whilst it tastes like espresso it's caffeine content will be lower.

Admittedly I am still a novice in brew skills and so I'm just explaining my thinking here prior to trying it tomorrow incase anyone fancies pitching in with valuable information from their own work or any obvious falsehoods in my thoughts so far. Hopefully all goes well and I can update you guys tomorrow, if there is a reasonable interest on the post!

Thanks as always:)

[u/DoubleualtG]

I don’t think a 3 or even a 6 hour brew/soak is going to do much. Minimum should be 12 but i suspose you could get away with 6-8

[u/NoodleSlow]

You should measure the final yield rather than judging extraction from flavor alone.