Tuesday, March 22, 2016

Cold brewing coffee by agitating all night

Making coffee with boiling or near boiling water vapourizes a lot of the nice smelling volatile compounds (so the room smells nice but you don't get to enjoy them from your cup) and changes other compounds. Overnight in the refrigerator makes very weak coffee (doesn't extract much), but has promising taste. One could probably compensate by using a lot more coffee, but I don't like the inefficiency. So, I tried to extract more by agitating all night.
That is simply a geared electric motor slowly spinning a water bottle with some water and ground coffee inside. The 24V motor is powered by 3V from an adjustable wall wart. It's all put together in a temporary way because this is an experiment. I made it extra rigid because I don't want anything to shake apart as the water sloshes around. The plastic tub underneath is just in case something breaks or leaks.

In terms of darkness and caffeine, the coffee is similar to normal coffee made with hot water. It is less bitter, but it also lacks some other elements of flavour. I guess some aren't very soluble in cold water, and some are probably oils and not water soluble at all. The result isn't bad, but it's not better than my normal way of making coffee in a French press.

I wonder about using other liquids in this setup. Would milk extract more? What about extracting with oil? I wouldn't want to drink that, and it probably wouldn't extract caffeine because it is a water soluble alkaloid, but it might produce strongly coffee flavoured oil which is useful for cooking.

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