Ultrasonic Cold Brew
Ultrasonic cold brew explained: how UNSW Sydney engineers used 38.8 kHz sound in an espresso basket to make cold brew in under three minutes, and how it tasted.
Contents
- Method
- The short version
- How does ultrasonic cold brew work?
- How fast is it, and how much does it extract?
- Does ultrasonic cold brew taste as good?
- How was it made in the study, step by step?
- Can you make ultrasonic cold brew at home?
- What came next?
- Ultrasonic cold brew vs other methods
- Words in this guide
- Questions & answers
What is ultrasonic cold brew?
Ultrasonic cold brew is an experimental method from UNSW Sydney that uses sound waves instead of time. Researchers fitted an espresso machine basket with a transducer that sends 38.8 kHz ultrasound through room-temperature coffee, cutting cold brew from 12 to 24 hours to under three minutes. Tasters found one to three minutes comparable to a 24-hour brew.
At a glance
- Difficulty
- Beginner
Method
Load the basket
In the UNSW setup, ground coffee goes into the brewing basket of a modified Breville espresso machine.
Use room-temperature water
The water is not heated. The study compared its samples with a traditional cold brew steeped for 24 hours at 4°C.
Switch on the ultrasound
A bolt-clamped transducer and metallic horn send 38.8 kHz sound waves into the basket walls, creating cavitation and mixing in the coffee bed.
Sonicate for one to three minutes
The researchers found one to three minutes gave coffee comparable to a 24-hour cold brew. One minute was slightly under-extracted and three slightly more bitter.
Collect the brew
The brewed coffee is collected like an espresso, ready to drink cold or use as a base.
Ultrasonic cold brew is an experimental way of making cold brew in minutes rather than hours, using ultrasound instead of a long steep. It was developed by engineers at UNSW Sydney in Australia, led by Dr Francisco Trujillo, and published in the journal Ultrasonics Sonochemistry in 2024. You’ll also see it called sonic or sonicated cold brew. This page explains how it works and what the research found. It isn’t something you can make at home yet.
The short version
- Sound instead of time: 38.8 kHz ultrasound speeds up extraction in room-temperature water.
- Under three minutes, against 12 to 24 hours for a normal cold brew.
- Built on an espresso machine: a modified Breville, with the basket turned into an ultrasonic reactor.
- Taste: one to three minutes was rated comparable to a 24-hour cold brew.
- Not on sale: it’s a patented research system aimed at coffee machine makers.
How does ultrasonic cold brew work?
Normal cold brew is slow because cold water extracts coffee slowly. The UNSW team’s idea was to speed that up with sound.
According to UNSW, the team took an existing Breville espresso machine and added its own patented sound transmission system. A bolt-clamped transducer is connected to the brewing basket through a metallic horn, turning a standard espresso filter basket into an ultrasonic reactor. Sound waves at 38.8 kHz are injected at several points through the basket walls.
The paper explains what that does inside the basket:
- Acoustic cavitation: the sound creates many regions of cavitation in the coffee bed.
- Acoustic streaming: it mixes the coffee and water and speeds up mass transfer, which is the movement of flavour and caffeine out of the grounds.
How fast is it, and how much does it extract?
| Measure | Result in the 2024 study |
|---|---|
| Brew time | Under 3 minutes, against 24 hours without ultrasound |
| Extraction yield at 100 W (33% basket loading) | Up from 15.05% to 33.44% |
| Caffeine at 100 W (67% basket loading) | Up from 0.91 to 1.84 mg/mL |
| Total fatty acids (33% basket loading) | Up from 1.16 to 9.20 mg/mL |
The paper also found that extraction was more efficient with less coffee in the basket. “Basket loading” is how full the basket is.
Does ultrasonic cold brew taste as good?
The study’s samples were tasted by a trained panel at the Queensland Alliance for Agriculture and Food Innovation, part of the University of Queensland, UNSW says. They compared three coffees:
| Sample | How it compared with 24-hour cold brew |
|---|---|
| Ultrasonic, 1 minute, room temperature | Similar flavour, aftertaste and texture, but lower aroma intensity, suggesting slight under-extraction |
| Ultrasonic, 3 minutes, room temperature | Similar dark chocolate aroma and intensity, but slightly more bitter |
| Traditional, 24 hours at 4°C | The reference |
Dr Trujillo’s conclusion was that one to three minutes is ideal, “depending on the interest of customers”. The paper calls the 1 and 3 minute coffees “almost undistinguishable” from the 24-hour brew.
How was it made in the study, step by step?
This is the research process, not a home recipe:
- Load ground coffee into the basket of the modified espresso machine.
- Use room-temperature water. Nothing is heated.
- Switch on the ultrasound, sending 38.8 kHz sound through the basket walls.
- Sonicate for one to three minutes.
- Collect the brew like an espresso.
The UNSW release doesn’t give a coffee dose or grind for its tests.
Can you make ultrasonic cold brew at home?
Not yet. The method depends on the team’s patented reactor, which isn’t on sale. Dr Trujillo told UNSW the team wants the technology used “by companies that already manufacture coffee machines” so people can make it at home. Until then, a regular cold brew or a Japanese iced coffee is the practical option.
What came next?
In 2026, Inside FMCG reported a follow-up from Trujillo’s team in the Journal of Food Engineering: an “ultrasonic espresso” made with room-temperature water. Brew times of two and a half to three minutes gave the best balance. In blind tests with about 100 regular coffee drinkers, people found no significant difference from conventional espresso, and preferred the ultrasound version of filter coffee overall. The team says the system could be scaled up for ready-to-drink coffee makers and could cut energy use by up to 75%.
Ultrasonic cold brew vs other methods
- Cold brew: the traditional 12 to 24 hour steep it aims to replace.
- Cold brew concentrate: a stronger steep for diluting.
- Toddy cold brew: the classic home cold brew system.
- Kyoto slow drip: cold water dripped through coffee over hours.
- Espresso: the machine the UNSW reactor was built on, using heat and pressure instead.
Explore every cold method in the cold chapter.
Words in this guide
- Extraction
- Extraction is the process of water dissolving flavour compounds out of ground coffee.
- Steeping
- Steeping is leaving ground coffee to sit in water so its flavour dissolves out, as in a French press or cold brew.
Questions & answers
What is ultrasonic cold brew?
An experimental way to make cold brew using ultrasound. Engineers at UNSW Sydney turned an espresso machine’s brewing basket into an ultrasonic reactor. Sound waves at 38.8 kHz speed up extraction in room-temperature water, so a cold brew takes under three minutes instead of 12 to 24 hours.
How long does ultrasonic cold brew take?
Under three minutes. The UNSW team tested one-minute and three-minute brews against a traditional cold brew steeped for 24 hours at 4°C, and concluded that between one and three minutes is ideal, depending on taste.
Does ultrasonic cold brew taste like normal cold brew?
Very close, according to the 2024 study. A trained panel rated the one-minute sample similar to 24-hour cold brew but lower in aroma intensity, suggesting slight under-extraction. The three-minute sample matched the aroma but was slightly more bitter.
Can I buy an ultrasonic cold brew machine?
Not that I could find. UNSW describes its patented sound transmission system as technology for companies that already make coffee machines, and a 2026 follow-up talks about scaling it up for industrial coffee producers. For now it’s research, not a product.
How does ultrasound make coffee brew faster?
The paper says the ultrasound creates regions of acoustic cavitation in the coffee basket, and acoustic streaming that mixes the coffee and water and speeds up mass transfer. At 100 W, it roughly doubled the extraction yield and caffeine concentration in the study’s tests.
What is ultrasonic espresso?
A 2026 follow-up from the same UNSW team, led by Dr Francisco Trujillo, published in the Journal of Food Engineering. It uses the same ultrasound approach with room-temperature water to make espresso-strength coffee in two and a half to three minutes.
Sources
- Coffee brewing sonoreactor for reducing the time of cold brew from several hours to minutes while maintaining sensory attributes. Ultrasonics Sonochemistry (Chiu, Naliyadhara, Trujillo et al., 2024)
- Hear that? That’s the sound of an ultrasonic cold brew coffee ready in under three minutes. UNSW Sydney
- Cold brew in minutes: Researchers take the heat out of coffee processing. Inside FMCG
General guidance only. Not medical, food-safety or professional advice. Always follow your equipment's own instructions.