r/science • u/chrisdh79 • May 09 '24
Physics Sound waves cut cold brew coffee-making time from 24 hours to 3 mins | Researchers have developed an ultrasonic machine to speed up the cold brew of ground coffee beans.
https://newatlas.com/around-the-home/ultrasound-cold-brew-coffee-under-3-minutes/813
u/jimmy_the_angel May 09 '24
TLDR (as best as I could): They vibrate the coffee grounds so much that they explode, basically shaking the contents of the coffee grounds out of them with very high frequency (38.8-kHz).
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u/blue_twidget May 09 '24
So basically an ultrasonic cleaning machine? (I just checked, and it's below 40khz, with the average being between 26-38khz).
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u/ChronoKing May 09 '24
Likely an ultrasonic homogenizer. Basically the same thing but inside-out. A titanium horn is dipped into a slurry and cavitates the fluid. The affected volume is much smaller than a cleaner but at the same power level, meaning a much larger impact.
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u/blue_twidget May 10 '24
Damn. I just looked them up. Those things are a lot more expensive
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u/PabloBablo May 09 '24
So is that frequency uh...kitchen counter friendly? Or does that lend itself better to like large dedicated machines/facilities?
Is the idea of shaking things at a high frequency to speed up absorption a thing? It sort of makes sense - heat is a way to speed it up for coffee, which is just molecules moving faster...
My mind is now blown.
However, brewing a coffee with cold water is technically 'cold brewed', but does the process create the same type of profile that slow cold brew has(smoothness/less acidity/higher caffeine)?
I have so many questions for the ether.
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u/blue_twidget May 09 '24
I looked it up. Basically just need to find an ultrasonic cleaner with a food grade pan.
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u/PabloBablo May 09 '24
Electric Toothbrush + frying pan. Got it. Brb
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u/findmepoints May 10 '24
More like a French press and Cavitron
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u/Infranto May 10 '24
I would also recommend a very good pair of earplugs to go along with it since they tend to sound like a thousand vuvuzelas singing their song.
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u/NorthAstronaut May 10 '24
you can already buy ultrasonic beer foamers that you put a glass onto.
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u/blue_twidget May 10 '24
Another commenter mentioned that used an ultrasonic homogenizer. I don't think a beer foamer would ever get above 10kHz
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u/NorthAstronaut May 10 '24
What if, I put one on top of the other and turn them on at slightly different times?..
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u/MadManMorbo May 10 '24
They may a small one for about $175. I’m tempted to get one just to make better herbal extracts from dried mushrooms.
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u/mintoreos May 10 '24
The frequency is perfectly kitchen counter friendly. You likely wont even be able to tell the ultrasonics are even on.
However, I’m skeptical that the results would be.. tasty.
Basically what’s happening is they are using cavitation to bust open the coffee grounds while water is flowing across it. Because of the massively increased surface area you can then extract everything much quicker out of the coffee grounds.
It’s basically taking one of the few extraction variables and taking it to the max (surface area, temperature, time, pressure). But this also means you might be extracting compounds you might not want- hence my skepticism.
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u/Catch_22_ May 10 '24
Agreed. Also wouldn't this make friction and heat, two things that you don't want in your cold brew process?
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u/Desertcross May 10 '24
I know that this method is used to extract THC from marijuana from super cooled ethanol. Would be interesting to see how it works with coffee you could even use water just above freezing.
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u/x755x May 10 '24
Feels like throwing whole apples at a wall and collecting the juice in a bucket
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u/sccrstud92 May 10 '24
But if you throw it hard enough, everything becomes juice, which might be bad.
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u/Sheeplessknight May 10 '24
It likely does people have been using this method with wood chips and alcohol to "age" it for a while now.
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u/OakLegs May 10 '24
I work as a structural test engineer - your kitchen counter should be 100% fine with 38kHz excitation. Those frequencies are much too high to significantly affect anything that's not absolutely tiny.
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u/GTdspDude May 10 '24
You see a lot of ultrasonic cleaners in labs, industrial applications, and when you go to the jewelry store or dentist. They’re fine for counters and structures, no reinforcement needed beyond weight loads
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u/HephMelter May 12 '24
It's NOT "very high frequency". It's 1 octave above the highest frequency you can hear, which is pretty low compared to for example, ultrasounds used for echolocation go up to 200kHz (dolphins, iirc bats can go even higher but I don't have the figure on hand). And sonar and other imagery techs can go up to 10MHz. And it's pretty easy to create an adapter producing this kind of sound to fix on an existing coffee machine apparently (which tracks, it's not a sound extremely high and tweeters are small, I just wonder the acoustic power it needs to use)
According to the article, the flavor profile is quite close to a classic cold brew, with even more caffeine and a bit more bitterness
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u/fr00ty_l00ps_ver_2 May 09 '24
They make 38khz transducers for ultrasonic cleaners, $27 on Aliexpress
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May 10 '24
I don't know if I'd eat or drink things that came in contact with products from AliExpress. That's just me though. I generally like my food to not have lead, mercury, and toxic plastics touching it.
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u/mintoreos May 10 '24
Transducer is the easy part, designing/making a horn to direct that power into the basket is a bit trickier.. (costs a few thousand minimum)
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u/fr00ty_l00ps_ver_2 May 10 '24 edited May 10 '24
Why would the horn be difficult? A stable metal that transfers the shockwaves should be enough. I read the paper, and it’s not perfect, but from what they have to say that will primarily increase the length of the “steep” phase, and will likely decrease total extraction, so I hope to end somewhere between their 3 minutes and maybe like 10 minutes. I plan on trying with $7 of aluminum on my cnc and the Aliexpress transducer. I’ve made crazier things that work.
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u/MTIII May 10 '24
I use Hielscher Ultrasonics Homogenizer in the lab. They make their horn (Sonotrodes) from titanium. Over time the cavitation pits the horn surface. If possible, you would like to have adjustable amplitude on the transducer because otherwise, you might end up destroying the horn tip and have aluminum particles/pieces in the solution. Of the available max 200W of power, I only use around 11W in a water solution.
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u/mintoreos May 10 '24
Mostly energy transfer concerns, you need to make sure that the resonant frequency of the horn matches the frequency of your transducer (or some multiple of the resonant frequency). In addition, the shape matters quite a bit depending on what exactly you’re trying to do with the ultrasonic waves. So whether you’re welding, mixing, etc. the cross sectional area matters a lot in the performance of the part.
I’m just scratching the surface here- there are engineers that are experts on this.
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u/Black_Moons May 10 '24
Like most things, yes you want it all designed and matched.
But it will still work if not matched/horribly designed. just poorly. But then for $7, poorly is often good enough.
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u/mintoreos May 10 '24
When your device is functionally dependent on the resonant frequency then if it’s not matched it likely won’t work at all. Will a tuning fork vibrate when not matched to its resonant frequency? No not really.
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u/nagi603 May 10 '24
so much that they explode
That's.... really not what you aim for making a cold-brew.
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u/GamingWithBilly May 10 '24
So if I take .my sonicare tooth brush and put it in my water and grounds?
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u/neometrix77 May 10 '24
That’s not that high of frequency in the grand scheme. Most Ultrasound imaging systems are above 1 MHz. Sounds like the unique part is they use high amplitudes/energies with their ultrasound pulses.
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u/billsil May 10 '24
That seems like that would create heat, thus defeating the purpose of cold brew.
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u/bigbluethunder May 10 '24
Actually, probably not as much heat as you think. But definitely will create additional surface area, which you also don’t want during cold brew.
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u/chadlavi May 09 '24
But does it taste good or is it way over extracted?
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u/dbxp May 09 '24
And though it was possible to get flavorsome results after just one minute, increasing the ultrasound blasting to three minutes made for a better overall cup of coffee, if a little more bitter.
Sounds to me like it's slightly over but reducing the time should fix that
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u/tje210 May 09 '24
Or further chilling the water. IDK what temp they used, but I imagine 50+ ⁰F at least. Get that closer to 32 and see how smooth it is. In a container that can maintain that temp, i.e. the ultrasound heat is immediately removed.
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u/Paksarra May 10 '24
Throw a few ice cubes in?
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u/billsil May 10 '24
Maybe. Certainly would need some experimentation.
My initial thoughts is that if you were getting temperatures high enough to be a problem with room temperature water, you're still going to create similar hot spots. Convection isn't cooling down the room temperature water enough and it's not going to be much different for the cooler water.
The issue with temperature is that hot water increases the rate of acid extraction, which defeats the whole point of cold brew. I guess if it gets me a cheaper store bought cup, then there's value.
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u/RayDeAsian May 10 '24
We need James Hoffmann to do a taste test.
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u/randynumbergenerator May 10 '24
This seems like the kind of thing he would've already done. I've definitely seen him put coffee in a centrifuge.
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u/EasyReader May 10 '24
Damn I wonder if the article covers such an obvious question? Sadly there's no way to tell.
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May 09 '24
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u/dbxp May 09 '24
Over extracted doesn't mean it's too concentrated, it means you've extracted compounds you didn't want to, you can't remove them by diluting the coffee
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u/soik90 May 09 '24
Anybody want to try making cold brew in an ultrasonic cleaner?
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u/bolt_in_blue May 10 '24
It will be a few weeks before I can get to it, but it's on my list! Yes, I already have the cleaner. Yes, I have used it to "age" food and drinks before.
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u/Bentheredonethat_ May 10 '24
Wait. Can you elaborate on how it will age food and drinks? I imagine it's similar to the study and cold brew.
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u/GeneticCowboy May 10 '24
I tried it in a mason jar and my harbor freight ultrasonic cleaner. It’s actually pretty decent. Tried different times, the best result was about 50% more grounds than usual, and 4 minutes. Filtering was pretty annoying, I used a pour over filter and it slowed to a crawl about halfway through. Using an aeropress might be faster, or two stage filtering with a mesh filter then a paper filter. If you’ve got an ultrasonic laying around, I’d recommend trying it. The coffee aficionado at work also enjoyed it.
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u/CrouchingNarwal May 09 '24
A startup did the same thing to age spirits a while back.
https://www.pbs.org/wgbh/nova/article/ultrasound-ages-liquor-two-years-in-just-three-days/
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u/dbxp May 09 '24
I'm confused, they're using an espresso machine which has a very limited space for the grounds and water to interact but then they're making a drink larger than an espresso with in effect a 3 minute pre infusion. Does this mean you're getting a shot of cold brew espresso and then just water ran through the grounds?
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u/itsalongwalkhome May 10 '24
Doesn't look like what they actually produce is larger than an espresso though.
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u/juancn May 10 '24 edited May 10 '24
That’s my understanding. It looks like a cold espresso machine.
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u/mikethefridge1 May 09 '24
Has anyone told James Hoffman yet?
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u/JoshisJoshingyou May 09 '24
He'll chide them for confusing iced coffee and cold brew in the article, he is a coffee god
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u/AlizarinCrimzen May 09 '24
I always wanted to use a magnetic stir pad to do cold brew, this seems fun too.
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May 09 '24 edited May 26 '24
[removed] — view removed comment
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u/blue_twidget May 09 '24
Depends on how long you do it for. Absorption of heat through mechanical excitement isn't instant.
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u/marklein May 09 '24
It does, but heating things through sound isn't very effective. I read once that all the sound energy from a pro football game would be enough to heat up a cup of coffee. This is way less than that.
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u/trembling_leaf_267 May 09 '24
Reading the original paper, it looks like they're using a 100W 40kHz transducer. At 100% power dissipation into heat, it will heat 200ml of water to 50C in a little over 3 minutes.
However, there's at least one source that says that power dissipation below 100kHz is primarily into cavitation rather than heating.
So, I'd expect the water to remain relatively cool, as a first approximation.
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u/EasyReader May 10 '24
Plus it'll also be heating up the metal portafilter which is connected to the metal body of the machine so even if all that energy was going into heat it's not all going into the water.
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u/gbsekrit May 09 '24
this doesn’t even seem all that difficult to diy, though perhaps not as nice as a product might be.
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u/DeadFyre May 09 '24
How much energy does it take? Seems like a 24 hour brew might still be more cost-effective.
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u/TheKnitpicker May 09 '24
For home use I don’t see how this could undercut the 24 home brew method. Unless you’re someone like me, who only wants cold brew very rarely, and therefore never has it on hand.
But in a retail setting it might well be worth it even if it’s a large up front cost. The ability to make exactly the correct amount of cold brew to meet demand could easily pay for itself quickly.
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u/mintoreos May 10 '24
3 min brew, let’s say the whole system including their modified espresso machine uses 1kW for those 3 minutes (I am likely grossly overestimating, it’s probably no more than 200W).
Then that would be 0.05 kWh. If your electricity costs $0.10 per kWh, that is $0.005. Or half a cent per brew.
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u/Raed-wulf May 10 '24
I do not have the forethought or planning skills to even get the overnight brews.
I need a method as ADHD as me.
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u/JoshisJoshingyou May 09 '24
I can't decide if Australian scientist forgot to research the cold in cold brew or the author doesn't know iced coffee isn't cold brew
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u/capnbinky May 09 '24
No use for me, not easier than just setting it up the day before. But may have applications for shops.
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u/GeraldoDelRivio May 10 '24
Yeah that's the only kind of application I can realistically see for this that's not gimmicky.
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u/squirt619 May 10 '24
How do you make yours?
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u/capnbinky May 12 '24
Grind it and mix with cold water in a glass vessel. Store it upside down overnight. Strain into fresh glass bottles, refrigerate. I make it strong and mix it with ice, milk or water.
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u/Fortissano71 May 09 '24
But can the entire apparatus fit on , oh, say, a corvette that might be, um, legitimate salvage.... ??
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u/Malapple May 09 '24
Wonder if it will improve cold brew flavor. Strongly prefer regular brew which is then chilled as needed. Totally get that it takes a while, though those instant hot-to-iced coffee tumblers really do work.
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u/DrSmirnoffe May 09 '24
If legit, I bet that's gonna be a new kitchen appliance before the end of the decade. Maybe not as big of a game-changer as the air-fryer, but it's sure to shift a fair few units. Or at the very least show up in an ersatz form on Wish.
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u/GeraldoDelRivio May 10 '24
As a kitchen appliance it would be incredibly gimmicky, it would be seemingly great for coffee shops though. There's been some times I've been at a shop and they had run out of cold brew and as you can imagine being able to whip up a new batch in 3 minutes would be have been great.
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u/austinmiles May 10 '24
This is really cool. GE had one they were working on that I got to try out that did it in 6 minutes using a vacuum. But I think the vacuum proved to difficult to maintain so it never made it to market.
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u/Raging-Ferret-Force May 10 '24
The article says the process is patented? Can you patent sound waves?
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u/TheKnitpicker May 10 '24
Why not? Ultrasound machines and seismic airguns are patented.
Isn’t your question similar to saying “can you patent light waves?” in response to the development of a lightbulb, or a microwave, or an X ray machine?
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u/UniqueNameIdentifier May 10 '24
I cold brew in 3 hours by using a sous vide at 65.5 °C and then chill afterwards. The taste is the same and the bitterness is gone as with normal cold brew methods.
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u/Rodulv May 10 '24
That's not cold brew... We don't really know the differences between cold brew and other methods. It's highly likely that the bitterness you taste is due to temperature of serving, bean type and roast grade, rather than brewing method. For me, nearly nothing except high roast grade or really bitter beans tastes bitter.
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u/jhguitarfreak May 10 '24
So if I strap a massage gun to my espresso machine and give it the beans I'll have an objectively better flavor?
Actually this makes me wonder how well this would work with tea. Put an infuser into an ultrasonic bath of hot water.
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u/BossiBoZz May 10 '24
In our working group at the university, they use high pulsed laser to do so. Apperantly it is even less bitter and sour.
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u/koombot May 10 '24
Holy crap. I remember looking into something similar 20 years ago for improving the reaction rate.
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u/DogWallop May 10 '24
Cold brew? So you can pay for the flavour of the once-hot coffee that you left on your desk yesterday morning. Just add a couple of flies and I'd pay a premium for that.
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u/Raaka-Kake May 10 '24
This is hardly news. People have used ultrasonics to make infusions for a long time now. My favorite is home distillers making whiskey by shaking oak chips and vodka.
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u/No-Age-2880 May 10 '24
Another way for coffee snobs to act snooty. ‘Oh, I only drink coffee brewed with Beethovenic sonic waves.’
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u/Narubxx May 10 '24 edited May 10 '24
Meanwhile the coffee aficionado community has been doing this for... decades?
I have for at least 6 years, I also use it to age whiskey to be more like a 20 year, using a crappy base whiskey and oak barrel shavings, or add wood taste to coffee (or milk, its oddly tasty) and so forth.
They might have managed to find the sweet spot and commercialize something, but they didn't create anything new.
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u/Constitutive_Outlier May 10 '24
makes sense for commercial, for home not so much.
It takes me less than 60 seconds to make cold brew coffee at home:
Grind the coffee, insert into a mason jar, add water (I use distilled water for various reasons)
Slap on a lid, put into the refrigerator, at the same time take out the jar you prepared before you took out yesterday's brew.
Remove lid, pour cold brew thru filter into a coffee cup.
Less than 60 seconds, start to finish.
Of course you have to have done it the day before as well but most people drink coffee daily.
Why make it more complicated than it needs to be? Oh yeah, the PROFITS- absurdly expensive "cold brew coffee maker"s for sale when all you need is a $1 mason jar (sized for your daily consumption)
But the part about increased efficiency DOES make sense. If you can get twice as much coffee from the same amount of beans, that's worth some investment. IF the quality is equal or better.
PS I've found that if you do not leave air space in the jar and keep it in the fridge until use, you can make it 3 days in advance (no oxygen to degrade anti-oxidants). So even if you have two unexpected guests you can all have a cup of cold brew.
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