That’s not exactly what it’s doing. Cavitation is when when the pressure of a liquid reduces below the vapour point. Heat isn’t involved the liquid “boils” because the vapour point decreases with reduced pressure.
🤷♂️ Tomato / Potato. Cavitation occurs (the bubble formation) at a temperature below 100C, yes. As the steam bubble shrinks, very high temperatures are reached (super-heated steam). All of that energy, plus the latent heat of condensation is released back into the fluid. At that instant, there is a very small yet-to-be-mixed portion of liquid that may be near the boiling point. That small portion of fluid may undergo a warm-brew process as it cools and mixes. I’m kind of conceptualizing this brewing process like: what if you could heat, mix, and cool the coffee all at once everywhere. But I’ve never observed cavitation and bubble collapse with an ultra high-speed microscope camera, so my concept may be off a bit. I have seen photos of what it does to hardened steel hydropower turbines.
My next question would be, what if you start with ice water? That may give you something like true cold-brew. Another factor to consider is that I believe most cold brew is very oxidized. It might be interesting to try ultrasonic degassing for some period of time before the grounds are added, to see how much of the cold brew flavor is just oxidized coffee.
That’s not exactly what it’s doing. Cavitation is when when the pressure of a liquid reduces below the vapour point. Heat isn’t involved the liquid “boils” because the vapour point decreases with reduced pressure.
🤷♂️ Tomato / Potato. Cavitation occurs (the bubble formation) at a temperature below 100C, yes. As the steam bubble shrinks, very high temperatures are reached (super-heated steam). All of that energy, plus the latent heat of condensation is released back into the fluid. At that instant, there is a very small yet-to-be-mixed portion of liquid that may be near the boiling point. That small portion of fluid may undergo a warm-brew process as it cools and mixes. I’m kind of conceptualizing this brewing process like: what if you could heat, mix, and cool the coffee all at once everywhere. But I’ve never observed cavitation and bubble collapse with an ultra high-speed microscope camera, so my concept may be off a bit. I have seen photos of what it does to hardened steel hydropower turbines.
My next question would be, what if you start with ice water? That may give you something like true cold-brew. Another factor to consider is that I believe most cold brew is very oxidized. It might be interesting to try ultrasonic degassing for some period of time before the grounds are added, to see how much of the cold brew flavor is just oxidized coffee.