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Cold brew coffee in 3 minutes using acoustic cavitation

unsw.edu.au

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Re: Cold brew coffee in 3 minutes using acoustic cavitation

#171

Post by eternauta3k »

bunderbunder wrote: post #165
marcoalopez wrote: post #104

Earlier quoted context omitted.

This is only partly true. Because low-temperature extraction is much less efficient, it requires a much longer immersion/exposure time than hot extraction at ambient or slightly higher pressure. One of the effects of this type of cold extraction is the oxidation of the coffee, which is much greater with this method, giving the coffee an oxidised taste which, although not bad in itself (nothing is set in stone about p…

Definitely. Though the oxidation seems different? I don't find cold brew to taste "stale" the way hot brewed coffee that's been stored overnight in the refrigerator does. I have a bunch of kegging equipment that I don't use anymore because I've lost my taste for beer, and I keep wanting to see what happens if I use it to make cold brewed coffee under a bed of CO2. Also, y'know, coffee on tap at home.

Won't the CO2 make the water acidic?

Re: Cold brew coffee in 3 minutes using acoustic cavitation

#172

Post by fuzzzerd »

D13Fd wrote: post #109
dahart wrote: post #17

Recently I discovered that many coffee shops, maybe half in my sampling of a couple dozen in different cities, are selling cold coffee (brewed hot, then refrigerated) under the name cold brew, and even the ones that actually cold-brew them seem to be under the impression that it needs to be served cold. I was laughed at in one hipster joint for asking for a steamed or warmed cold-brew, and another one initially refus…

I drink only cold brew normally, and I've noticed this as well. It's 50/50 whether you will get actually cold brew at any given coffee shop or just iced hot-brew coffee, which tastes different and has much less caffeine. Cold brew needs a new name or it will likely fade away over time.

There's nothing wrong with the name cold brew. It describes the difference from "standard" coffee. It is the charlatans selling warm brew over ice that devalue it.

As someone that greatly prefers coffee brewed cold and served on ice, I hope it doesn't fade away, because without it I have a lot less reason to get coffee out as opposed to at home.

Re: Cold brew coffee in 3 minutes using acoustic cavitation

#173

Post by spython »

Or you could use a (quite affordable) ultrasonic machine designed for gentle cleaning of jewelry, dentures, glasses..

I've used one to extract fragrance from biological material for an artistic project[0], and it worked really well. Instead of having to wait for a few weeks for a tincture to finish, you put the same tincture (alcohol and material you want to extract fragrance from) into a plastic bag for just 15 minutes. Sure, it smells not quite the same, but the speed is often worth it. I've even heard about some guy trying to turn vodka into whiskey with an ultrasonic machine and wood chips.

There are quite a few ultrasonic machines on the market. I've tried EMAG and multiple Chinese no-name machines that are just as powerful but cheaper. Sadly the no-name machines are quite a bit louder - you can't stay in the same room while it's running basically. Still, they all work well for this kind of fast and dirty extraction.

[0] https://rybakov.com/blog/smelling_cz/

Re: Cold brew coffee in 3 minutes using acoustic cavitation

#174

Post by eichin »

floatrock wrote: post #38
htrp wrote: post #12

Earlier quoted context omitted.

I think the idea is that the vibration transmits through the entire filter. The question is whether it's geometry/frequency specific

The embedded youtube video at 0:58 shows a laptop screen with some pretty fancy-looking simulation jiggles and heatmaps on what looks like an espresso filter. It also looks like a PDF of a paper, so presumably they have a paper that talks about the geometry/frequency interactions.

The article includes a link to the paper, which has simulation models of the acoustics, showing pressure levels and areas where cavitation can occur. (I didn't see anything about heating from dissipating the acoustic energy, though?)

Re: Cold brew coffee in 3 minutes using acoustic cavitation

#175

Post by ch4s3 »

rrrrrrrrrrrryan wrote: post #140
cout wrote: post #46

Earlier quoted context omitted.

As I understand, the serving temperature of coffee does have an effect on perceived acidity (which is NOT the same as pH), though I don't understand the science behind it. Here is one paper that claims it is due to release of volatiles at higher temperatures: https://www.sciencedirect.com/science/article/abs/pii/S03088... If that's correct, then warming the coffee again to that temperature would again speed up the re…

As a complete layman, when I tried tossing cold brew into the microwave it ended up tasting pretty gross. Like, jarringly so. I won't pretend to know the science behind it, or perhaps I warmed it differently than what the parent poster does, but I definitely sympathize with the barista's hesitation in his story.

Yeah, there are still a lot of dissolved coffee solids in cold brew that get further extracted if heated. There are also a lot of volatile compounds that break down when heated. The idea that you can just reheat coffee, even cold brew and have it taste the same is just ridiculous.

Re: Cold brew coffee in 3 minutes using acoustic cavitation

#176

Post by aspenmayer »

SamBam wrote: post #113
petre wrote: post #101

Earlier quoted context omitted.

That reminds me of the Soul Kitchen movie when a client of a fancy restaurant asked for a hot gazpacio. The waiter escalated to the chef who calmly explained to the client what a gazpacio is. After the client insisted, shouting at him, the chef refused driving his knife into the client's table. https://youtu.be/rQ61MfRBSQg

> We had gazpacho soup for starters... I didn't know that gazpacho soup was meant to be served cold. I called over the chef and told him to take it away and bring it back hot! So he did... the looks on their faces still haunt me today! I thought they were laughing at the chef, when all the time they were laughing at me as I ate my piping hot gazpacho soup! I never ate at the Captain's table again. That was the end of…

Red Dwarf is one of the most unhinged shows I’ve seen, in the best way. Nice reference, as I was also thinking of hot gazpacho soup, but had forgotten this scene until you reminded me of it.

Re: Cold brew coffee in 3 minutes using acoustic cavitation

#177

Post by eichin »

knicholes wrote: post #69

Does anyone know what make this better than just stirring for three minutes?

The paper lists many things they tested for, but the fascinating one is that the coffee oils and water get emulsified which isn't going to happen with any level of stirring below "purée" :-)

Re: Cold brew coffee in 3 minutes using acoustic cavitation

#178

Post by eternauta3k »

0xbadcafebee wrote: post #149

So, to simplify, we could take a large mason jar and attach to the bottom a magnet and wire coil attached to a power source, and just pump sound waves into a glass jar of water and coffee grounds. Effectively it's a speaker that holds coffee. Should have the same effect

If the cavitation really is important then no, it won't have the same effect. But maybe the cavitation is not important! Try it out and report back.

Re: Cold brew coffee in 3 minutes using acoustic cavitation

#179

Post by Spivak »

dmix wrote: post #156
WirelessGigabit wrote: post #130

Earlier quoted context omitted.

> I’m baffled that so many people who sell coffee for a living, think they know a lot about it, and act like coffee snobs, don’t seem to understand what cold brew even is. Anecdotally, this is something I've experienced in the USA more than in Europe. When I ask a question in store a lot of times I get the feeling that the person answering considers themselves an expert and quickly make claims that I know for a fact…

You're saying Europeans are less smug than Americans?

It's less about smugness and more that customer-service people are expected to behave like AI and always have an answer whether it's correct or not. I hope at some point we can drop the facade and "I don't know man, I just run the till. Do you want coffee or not?" becomes an acceptable response.

Re: Cold brew coffee in 3 minutes using acoustic cavitation

#180

Post by elevatedastalt »

tracker1 wrote: post #168
elevatedastalt wrote: post #139

Earlier quoted context omitted.

The emperor really has no clothes when it comes to food fads. And pricing is a completely orthogonal and obtuse concept too. Cold brew is putatively low effort and low cost. Just let coffee grounds soak in water overnight and you have cold brew. But it's often charged more than regular coffee or espresso-based drinks, which a) use more expensive equipment b) need more skilled operation c) more material [milk etc]

As to C, that applies to cold brew just as well as hot brewed coffee.

Possibly, but I've seen cold brew served mostly just by itself or just some syrup / cream, as opposed to cappuccinos / lattes which need much more milk.
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