As a continuation of the attempts at rapid infusion, this experiment tries to mimic the one Dave Arnold demonstrated in the first public Harvard lecture on Science and Cooking in which he created coffee vodka.
The Theory and Technique
The most common way for infusing coffee is by brewing it in hot water however, if you’re wanting to drink the coffee cold, letting it cool will result in an overwhelming astringent flavour. This is due the chlorogenic acid in the coffee forming quinic acid as it cools. In order to reduce this apparent acidity the coffee needs to be brewed in a way that does not involve heat. Cold brewing coffee is easy enough but it takes considerably longer (sometimes 12-24 hours) so, just as with the vanilla extract experiment, this aims to drastically reduce that time to a few minutes. As this builds upon the vanilla extract experiment the theory and technique are the same so no need to repeat that here however it is probably worth mentioning that the N2O will add a slight sweetness to the coffee (whereas using CO2 would add a metallic-like tang).
- 0.5L cream whipper
- 8g N2O chargers
- Coffee grinder
- Measuring jug
- Coffee filters
- 0.5L Smirnoff vodka
- 500g Coffee beans
- Something to compare against – Since the coffee vodka is made to go with cream and milk the comparator for this experiment would be a White Russian which is a mixture of Kahula, cream, full fat milk and vodka.
- Grind 500g of fresh coffee beans as fine as possible and add into the cream whipper.
- Add 0.5L of vodka to cream whipper.
- Seal up the whipper, add charges, and give it all a bit of a shake.
- Leave to sit for 2 minutes.
- Keeping the whipper upright to minimise blockages, vent all of the gas in one go. This will be extremely messy so you’ll want to have something to catch all the foam. Even once you think all the gas has been vented be sure to give the handle an extra squeeze or two as it’s possible the grounds may have blocked the valve. You really don’t want to be opening the canister while it’s still pressurised as it’ll spew the contents everywhere.
- With the canister vented it’s time to filter the coffee grounds from our vodka solution using the filters. You’ll probably want to filter the mixture at least twice.
Taste Test, Conclusion and the Future
For the taste test we added some full fat milk and cream to 25ml of coffee vodka and mixed some White Russians (25ml Kahula, 25ml vodka, milk). The White Russian was inherently a lot sweeter due to the Kahula while the coffee vodka was extremely bitter and intense. This is likely due to having used expresso beans so for future testing a less intense bean would be better. Better results would probably be achieved if we ground the beans finer and did an additional filter process.
(Photographs courtesy of Heather Sullivan)