We wanted to test the pH of our cold brew coffee. For things like this I generally ask my friend Sean, who is a chemistry genius and PhD student to help.
Long story short Sean found that a lighter roast is more acidic (pH 5.5) than the regular blend, which is roasted to second crack (5.8) but the concentrate was slightly more acidic at pH 5.7.
Makes sense, right? Pertinent information.
But then Sean wondered what would happen if we put the cold brew through his extruder…
Now his extruder is a custom built device kind of like an aeropress on crack. It’s a heavy set steel cylinder that is screwed in place over a filter. At the bottom is a little tube for liquid to come out.
You put what you want in the cylinder, seal it up and then pump nitrogen into it. The only space for whatever it is you put in can go, is through your filter.
The filter was a 200 nanometre film. That is, one thousand times smaller than the width of a human hair.
When I filter Harpoon Cold Brew I use a 40 micron mesh. So I’m wondering what will happen here – will anything come out at all?
My hypothesis is that it will come out clear, the dissolved coffee particles will surely being larger than 200 nanometers, so only water will come out.
We pop 10 ml Harpoon concentrate into the extruder and pump it with gas.
And this is what came out:
Nitrogenated cold brew. There was no residue on the filter.
This means (as far as this rudimentary, quick, unwritten, unscientific test is concerned):
- When coffee dissolves into liquid it fully dissolves i.e. there are no partcles that get caught in a 200 nanometer film
- You can nitrogenate cold brew pretty quickly if there’s enough pressure (not sure what pressure it got up to)
- We couldn’t sample this as we didn’t sterilise the equipment before doing it. I imagine it wouldn’t have tasted much different, just creamy from the Nitrogen
So there you have it: Pseudoscience at it’s finest!