If you are a coffee junkie and love to drink your cuppa to your exacting specifications, you probably don’t like to drink it cold, even though the chilled version sliding down your throat and creating that soothing sensation in your gut is very welcome in these hot summers. Cold coffee isn’t ‘coffee’, because it is the hot version made cold by adding ice cubes or chilling it in a refrigerator.
Truly cold coffee is made by ‘cold brew’ — steeping the grounds in water that is either at room temperature or lower, for about 24 hours. But few take the trouble of this immersion brewing.
Now scientists are experimenting with newer methods of brewing coffee. One — this sounds truly crazy — is to pump ultrasounds into the coffee basket of an espresso machine. Several scientists have attempted this and produced scientific literature.
When high intensity sound waves pass through the liquid (any liquid), it creates regions of compression and rarefaction. In the rarefaction regions, due to fall in pressure, gas or vapour pockets form, creating bubbles. These bubbles grow bigger and explode, creating a force that fractures the cell walls of coffee grounds, releasing the intracellular content. You can have a nice ‘cold brew’ coffee in minutes.
The coffee that comes out of the process is, according to scientists, “tasty”.