Everything about this ‘news’ sounds sus.
But they are wearing lab coats.
Ultrasonic tech is so cheap & sold everywhere.
And like all agitation, it transfers heat (not like a microwave, as most heat is transferred to surrounding air, but heats up the liquid, and it mostly does so by heating/getting absorbed by the dense objects, ie grains, mostly surface).
Also, in case this somehow didn’t exist for decades, all of it is just a bit better way of stirring - you can make cold brew by just mixing/shaking stuff. The coarser the grind the longer it would take to extract efficiently tho (but efficiency isn’t rally the point, just taste?).
Ultrasounds accelerate extraction processes due to acoustic cavitation [8], [9]. When acoustic bubbles, also called inertial bubbles, collapse near solid materials, such as coffee grounds, they generate micro-jets with the force to fracture the cell walls of plant tissues, intensifying the extraction of the intracellular content [10].
Seems more involved than just aggressive stirring.
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.
Yes, that is exactly how ultrasonic cleaners are used, it basically gets abrasive on the surface (like scrubbing with like a hammering motion, but on a tiny level).
The size of the bubbles is determined by the frequency (the higher it is the smaller the bubbles with lower energy each, the lower it is the bigger are bubbles and more powerful each).
So, if you are cleaning a large flat metal sheet, then you can go lower frequencies to speed up the process, whereas you would want higher frequencies for more intricate objects so the amplitude is smol enough to get into all the tight spaces for bubbles to form.
38kHz is a very common for ultra cheap household various purpose cleaner (jewellery, fruit & veggies, glasses, delicate clothes, etc), I have a 50kHz buttplug shaped one (so you put in a container and is not itself part of one).
I agree this is the kind of thing I should find on YouTube, not in an academic journal. But the paper does go into a lot of detail about extraction efficiency, so I guess there might be some useful measurements.
I am curious about the taste. It should be somewhere in between cold brew and hot, but probably closer to cold. Cavitation is a violent process. On a micro scale it’s literally boiling. Then the steam bubble collapses and is instantly cooled because of an almost infinitely big heat sink. So when cavitation occurs near the coffee grounds, some of the extraction would be at much warmer temperatures, for a brief instant.
Oh, yes, I was making fun of the headline, about inventing.
With that in mind basically any experiment/measurement/scientific theory is some sort of invention, it’s just that we dont call it that.
Like, nobody invented the concept of tank, ppl “invented” materials, equipment, manufacturing & logistics/admin processes, etc that at one point allowed for a feasible “tank” to be compiled.
The authors used a 38 kHz transducer with 100W of power. For $60 you can get a 2L ultrasonic cold brewer - it’s 40 kHz and 60W: https://m.vevor.com/ultrasonic-cleaner-c_11064/vevor-316-stainless-steel-2l-ultrasonic-cleaner-industry-digital-heated-w-timer-p_010173559579
Exactly.
Everything about this ‘news’ sounds sus.
But they are wearing lab coats.
Ultrasonic tech is so cheap & sold everywhere.
And like all agitation, it transfers heat (not like a microwave, as most heat is transferred to surrounding air, but heats up the liquid, and it mostly does so by heating/getting absorbed by the dense objects, ie grains, mostly surface).
Also, in case this somehow didn’t exist for decades, all of it is just a bit better way of stirring - you can make cold brew by just mixing/shaking stuff. The coarser the grind the longer it would take to extract efficiently tho (but efficiency isn’t rally the point, just taste?).
From the paper.
Seems more involved than just aggressive stirring.
https://www.sciencedirect.com/science/article/pii/S1350417724001330
Cavitation is literally boiling, but the bubbles of steam are tiny, only last for an instant, and then collapse and cool back into the fluid.
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.
Yes, that is exactly how ultrasonic cleaners are used, it basically gets abrasive on the surface (like scrubbing with like a hammering motion, but on a tiny level).
The size of the bubbles is determined by the frequency (the higher it is the smaller the bubbles with lower energy each, the lower it is the bigger are bubbles and more powerful each).
So, if you are cleaning a large flat metal sheet, then you can go lower frequencies to speed up the process, whereas you would want higher frequencies for more intricate objects so the amplitude is smol enough to get into all the tight spaces for bubbles to form.
38kHz is a very common for ultra cheap household various purpose cleaner (jewellery, fruit & veggies, glasses, delicate clothes, etc), I have a 50kHz buttplug shaped one (so you put in a container and is not itself part of one).
I agree this is the kind of thing I should find on YouTube, not in an academic journal. But the paper does go into a lot of detail about extraction efficiency, so I guess there might be some useful measurements.
I am curious about the taste. It should be somewhere in between cold brew and hot, but probably closer to cold. Cavitation is a violent process. On a micro scale it’s literally boiling. Then the steam bubble collapses and is instantly cooled because of an almost infinitely big heat sink. So when cavitation occurs near the coffee grounds, some of the extraction would be at much warmer temperatures, for a brief instant.
Oh, yes, I was making fun of the headline, about inventing.
With that in mind basically any experiment/measurement/scientific theory is some sort of invention, it’s just that we dont call it that.
Like, nobody invented the concept of tank, ppl “invented” materials, equipment, manufacturing & logistics/admin processes, etc that at one point allowed for a feasible “tank” to be compiled.
Yeah, they didn’t even invent it. One company basically tried to do the same brewing technique commercially, but I guess they didn’t get the word out in time: https://www.engadget.com/osma-pro-cold-brew-coffee-machine-review-131552500.html
You can buy sub 50 moneys liion battery operated lil machines … that don’t use ‘sound pressure’ but ‘air pressure’ to brew (lul).
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Lab coats and pointing at a screen, give them the Nobel price already!
Not to mention the proper use of safety glasses whilst brewing coffee with 100W hi-tech.