Apologies if this has been discussed before ,search didn't turn up anything...
I am looking into ultrasonic mixing to create cold brew coffee, although without the required 8-12 hours, I'm hoping with additional agitation this can be reduced. I have experimented with 44Khz 60w ultrasonic transducer but it appears the frequency is to high, I have since ordered a lower 28Khz transducer and driver circuit. Links: Video 44Khz Photo of transducer and driver circuit
Anyway just wondering if anyone has tried this before? , and any thoughts and or suggestions. Look forward to hearing the forums thoughts.
Nice try at a novelty idea, but I think it's useless. A little transducer is going to do as much for your coffee as serenading the coffee jar with a radio. You could get more agitation by placing the cold brew on top of a loud bass speaker and play something with a beat. That might be followed by a visit from an equally agitated neighbor. Offer him a cup of awesome coffee & biscuit.
My intuition says tu use much lower frequency, like 2 cycles per minute and much more distance/travel. At first I thought more toward something around the frequency and intensity of a paint mixer. If you add cream, you could have a coffee whip. Nah, that's overkill.
How about one of those baby swings to gently sway your jar for a few hours. Some of those swings are a kinetic wind-up thing. I've seen a bar novelty that would rock from side to side, so that whatever was in the barrel would agitate as it rolled from one side to the other. The little barrel was the size of a pickle jar.
When I had high school chemistry, we had this little thing the size of a bean which would magnetically stir the beaker.
When I do a jar of cold brew, I just shake up the jar every couple hours if/when I happen to be within arms reach just to let it know it is loved. One of the benefits to cold brew is the very small energy footprint it leaves, smaller than manual drip, even.
How about one o' them hardware store paint-shakin' machines? ;-D
Heck, a decent blender...
How about those cold beverage machines they use to dispense stuff in some restaurants? Their designs vary. Some have mechanical agitators, some have fluid flowing over the top. A mod or two could make an interesting brewing device for cold/cool/tepid/lukewarm/warm brewing. 32
Pretty industrial looking stuff, however maybe you can glean some good info on what they are doing, frequencies involved, etc.
"Coffee leads men to trifle away their time, scald their chops, and spend their money, all for a little base, black, thick, nasty, bitter, stinking nauseous puddle water." ~The Women's Petition Against Coffee, 1674
wabbitt I fear you may be right on the frequency, although thats not stopping me from trying. My understanding is with cold brew it is the water extracts the water soluble parts from the coffee and this is diffused through the water. Agitation should increase the diffusion and make the coffee more uniformly distributed among the liquid, hopefully this will reduce the coffee concentration immediately around the coffee grounds and increase the rate of extraction?
rasqual Indeed i'm sure the paint mixers would increase the extraction rate although not sure I can convince the Mrs to put one in the kitchen... :P I'm not familiar with the design of commercial machines.. so can't really comment.
CoffeeRoastersClub Thanks , I have seen that article and my quest into ultrasonics was actually through looking at that site and using it in Biodiesel production, which I believe Hielscher use around 20Khz, although I can't seem to find the reference back too this.
An interesting article seems to support that I'm on the right track dropping the frequency to 28Khz, although to achieve a rapid cold brew make be asking too much? APPLICATION OF ULTRASOUND THERMAL PROCESS ON EXTRACTING FLAVOR AND CAFFEINE OF COFFEE Ultrasonics used in biodiesel reduce the reaction time by a factor of 100 compared to mechanical mixing, although this is pure chemistry I'm hoping some of this theory will transfer.
I appreciate all the feedback/thoughts and open to any suggestions that may improve the extraction rate and or taste.
Posted Mon Feb 2, 2015, 7:20am Subject: Re: Ultrasonic Brewing
Neat.... ultrasonics do some unobvious things:
I've excerpted, here, the abstract from this paper:
Applications of ultrasound in food technology: Processing, preservation and extraction Farid Chemat, , Zill-e-Huma, Muhammed Kamran Khan
Cavitation seems to play a major role here, in ways that simple mixing just cannot do. Depending upon the power and frequency you use, you may actually destroy or alter favor components in your coffee. But, then again, you may enhance them. Your palate will know.
They actually made sonic espresso. They used a really powerful sonicator.
"Abstract Ultrasound is well known to have a significant effect on the rate of various processes in the food industry. Using ultrasound, full reproducible food processes can now be completed in seconds or minutes with high reproducibility, reducing the processing cost, simplifying manipulation and work-up, giving higher purity of the final product, eliminating post-treatment of waste water and consuming only a fraction of the time and energy normally needed for conventional processes. Several processes such as freezing, cutting, drying, tempering, bleaching, sterilization, and extraction have been applied efficiently in the food industry. The advantages of using ultrasound for food processing, includes: more effective mixing and micro-mixing, faster energy and mass transfer, reduced thermal and concentration gradients, reduced temperature, selective extraction, reduced equipment size, faster response to process extraction control, faster start-up, increased production, and elimination of process steps. Food processes performed under the action of ultrasound are believed to be affected in part by cavitation phenomena and mass transfer enhancement. This review presents a complete picture of current knowledge on application of ultrasound in food technology including processing, preservation and extraction. It provides the necessary theoretical background and some details about ultrasound the technology, the technique, and safety precautions. We will also discuss some of the factors which make the combination of food processing and ultrasound one of the most promising research areas in the field of modern food engineering."
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