Ultrasonic Herbal Oil Infusion: The Science of Cavitation
Can ultrasonic waves really speed up the process of infusing herbs into oil?
Traditional herbal oil infusion is wonderfully simple.
Place plant material into a carrier oil, give it time, and allow naturally occurring compounds to gradually migrate from the plant into the oil.
Depending on the herb, the oil, the preparation and the desired result, that process can take days or even weeks.
But what if we could dramatically accelerate the process without simply turning up the heat?
That is where ultrasound enters the picture.
In this Boner's Botanicals experiment, we're using an ultrasonic cleaning bath to help infuse herbs into oil. And while the machine may look deceptively simple, something rather interesting is happening at the microscopic level.
The key word is:
Cavitation.
Watch the Experiment
In the video above, we demonstrate the process of using an ultrasonic bath to help extract plant material into oil.
But what's actually happening inside that machine?
To understand that, we have to go smaller.
Much smaller.
What Is Ultrasonic Extraction?
Ultrasound refers to sound waves above the range of human hearing.
When sufficiently powerful ultrasound passes through a liquid, it creates alternating cycles of compression and rarefaction—essentially rapid fluctuations between higher and lower pressure.
Under the right conditions, those pressure changes can produce tiny bubbles within the liquid.
These are called cavitation bubbles.
The bubbles form, grow and eventually collapse.
And that collapse is where things get interesting.
Cavitation: The Invisible Storm
Imagine millions of microscopic bubbles forming and collapsing throughout a liquid.
When a cavitation bubble collapses, the surrounding liquid rushes inward.
That collapse can produce extremely intense, localized mechanical effects—including shock waves, microjets, turbulence and shear forces.
Scientists have studied these effects extensively in ultrasound-assisted extraction.
The result is sometimes described as an invisible microscopic storm.
The plant material is sitting in the middle of it.
And plant tissue isn't necessarily an impenetrable fortress.
What Does Cavitation Have to Do With Herbs?
Plant tissues are complex structures.
Inside leaves, flowers, stems and other plant material are compounds that can include volatile aromatic compounds, pigments, phenolics and other phytochemicals.
Under conventional maceration, those compounds migrate into the surrounding oil largely through diffusion and mass transfer.
Ultrasound can change the physical environment surrounding that plant material.
The mechanical effects associated with acoustic cavitation can:
-
disrupt plant structures
-
increase permeability
-
promote mixing
-
reduce boundary layers around plant particles
-
improve contact between the plant material and surrounding liquid
-
accelerate mass transfer
In simple terms:
Ultrasound can make it easier for the surrounding liquid to interact with the plant material.
That can mean faster extraction.
But Here's an Important Scientific Detail
There is a common misconception about ultrasonic baths.
You can see bubbles and turbulence in the water surrounding your container and assume those exact bubbles are exploding inside the oil.
We shouldn't make that assumption.
In a typical ultrasonic cleaning bath, the transducers generate ultrasound in the bath liquid, usually water.
If your herbal oil is contained inside a separate glass vessel, the ultrasonic energy has to travel through the bath liquid, the container and then into the material being treated.
How much acoustic energy actually reaches the oil—and what kind of cavitation occurs within that oil—depends on the equipment, container, liquid properties, geometry, frequency and operating conditions.
That's why the safest scientific description is:
An ultrasonic bath exposes the herbal oil and plant material to ultrasonic energy, while acoustic cavitation and related mechanical effects are known to enhance extraction processes.
That's more accurate than simply saying:
"The bubbles are exploding inside the oil."
Science is more interesting when we don't have to exaggerate it.
Researchers Have Actually Infused Herbs Into Oil Using Ultrasound
This isn't merely a theoretical idea.
Researchers have experimentally used ultrasound to accelerate the transfer of compounds from plant material directly into oils.
One particularly relevant study investigated the ultrasound-assisted maceration of rosemary and basil in extra-virgin olive oil.
The researchers optimized ultrasound-assisted processing and compared it with conventional maceration.
For rosemary, the optimized ultrasound-assisted process used approximately 37 minutes of treatment at 35°C.
For basil, the optimized treatment took approximately 10 minutes at 30°C.
The conventional comparison involved maceration periods measured in days.
The researchers analyzed the resulting oils for volatile compounds, phenolic compounds, antioxidant capacity, oxidative stability and other chemical characteristics.
They also examined the physical effects of ultrasound on the plant material using scanning electron microscopy.
Their conclusion was that ultrasound-assisted maceration could substantially accelerate the aromatization process compared with conventional maceration.
That's a pretty significant difference.
Days versus minutes.
But there's another study that gets even closer to what we're demonstrating.
Sage, Ultrasound and Oil
In a 2023 study, researchers investigated ultrasound-assisted extraction of compounds from sage (Salvia officinalis) directly into fish oil.
The researchers used an ultrasonic bath operating at 40 kHz and tested different power levels and treatment times.
They examined compounds including:
Carnosic acid
Carnosol
Rosmarinic acid
and total polyphenols.
The researchers found that ultrasound-assisted maceration successfully transferred compounds from the sage into the oil.
Under their tested conditions, the highest measured amounts of carnosic acid and carnosol occurred after 60 minutes of ultrasonic treatment at the higher tested power.
This is particularly interesting because the researchers weren't extracting the sage into water or alcohol first and then transferring it into oil.
They were investigating the direct movement of plant compounds from sage into oil.
That's essentially the same broad concept we're exploring here.
Of course, their specific results shouldn't be assumed to apply identically to every herb, carrier oil or ultrasonic machine.
Different plants contain different compounds.
Different oils behave differently.
And different ultrasonic equipment produces different acoustic conditions.
Why Would Ultrasound Make Extraction Faster?
There are several mechanisms at work.
1. Mechanical disruption
Cavitation-related forces can physically disturb plant structures.
That can make compounds trapped within plant tissues more accessible.
2. Improved contact
Ultrasound promotes movement and mixing within liquids.
Better contact between the plant material and surrounding oil can improve mass transfer.
3. Increased permeability
The mechanical effects associated with ultrasound can increase the accessibility of plant tissues and cellular structures.
4. Enhanced mass transfer
Once compounds are released from the plant matrix, they must move into the surrounding liquid.
Ultrasound can improve the conditions under which that transfer occurs.
5. Particle disruption
Depending on the intensity and duration of treatment, ultrasound can contribute to fragmentation and erosion of plant material, increasing the surface area available for interaction with the surrounding liquid.
Put all of those effects together and you have a plausible explanation for why ultrasound-assisted extraction can be considerably faster than passive maceration.
Explore WishGarden Herbs
Curious about liquid herbal blends and botanical preparations? Explore the range of herbal formulations from WishGarden Herbs.
Affiliate disclosure: Boner’s Botanicals may earn a commission from qualifying purchases through this link, at no additional cost to you.
Affiliate disclosure: Boner’s Botanicals may earn a commission from qualifying purchases through this link, at no additional cost to you.
It's Not Just About the Bubbles
Cavitation gets most of the attention—and deservedly so—but ultrasound-assisted extraction isn't necessarily a one-mechanism process.
Researchers describe several effects associated with ultrasound, including:
Cavitation
Acoustic streaming
Microstreaming
Shear forces
Microjets
Shock waves
Mechanical disruption
Improved mass transfer
The relative importance of these mechanisms depends on the system being studied.
That's another reason we prefer the term ultrasound-assisted extraction rather than claiming that cavitation is the only thing responsible.
How Fast Is Fast?
This is where things get really interesting.
In the rosemary and basil study, ultrasound-assisted maceration produced useful aromatization in approximately 37 minutes for rosemary and approximately 10 minutes for basil under their optimized conditions.
That was compared with conventional maceration periods of several days.
Another study involving sage used a 40-kHz ultrasonic bath and demonstrated extraction of measurable compounds directly into oil using treatment periods of only minutes to an hour.
But there's an important lesson here:
There is no universal "ultrasonic infusion time."
The optimum conditions depend on the system.
Variables include:
-
herb species
-
plant part
-
particle size
-
moisture content
-
oil type
-
herb-to-oil ratio
-
ultrasonic frequency
-
acoustic power
-
treatment time
-
temperature
-
container geometry
-
desired extracted compounds
In other words, an ultrasonic bath isn't a magic button.
It is a process tool.
And like any extraction method, it works best when the process is understood and controlled.
Temperature Matters
Ultrasonic extraction is sometimes described as a "non-thermal" extraction technique because ultrasound can achieve extraction without deliberately relying on high temperatures.
But that doesn't mean ultrasound produces no heat.
Energy introduced into a system can ultimately appear as heat, and temperature can rise during ultrasonic treatment.
This matters because many plant compounds are sensitive to temperature, oxidation and processing conditions.
The 2020 rosemary-and-basil study specifically optimized temperature along with ultrasound amplitude and treatment time.
The optimized temperatures were approximately 35°C for rosemary and 30°C for basil.
The sage study also intentionally conducted its ultrasonic treatment at approximately room temperature.
So if you're experimenting with ultrasonic herbal infusions, temperature is something worth watching rather than ignoring.
More Isn't Always Better
It can be tempting to think:
More power + more time = more extraction.
The science isn't quite that simple.
Ultrasound can improve extraction efficiency, but excessive intensity, prolonged treatment or uncontrolled temperature increases can potentially damage sensitive compounds or promote oxidation.
A recent review of ultrasound-assisted extraction notes that extreme processing conditions can produce undesirable effects, including degradation of sensitive phytochemicals and oxidation.
That means optimization matters.
The goal isn't necessarily to hit the plant with the strongest ultrasound possible.
The goal is to find the conditions that provide the desired extraction without unnecessarily damaging the material you're trying to preserve.
What Does This Mean for Herbal Oils?
For natural product makers, this is where the technology becomes especially interesting.
An herbal oil can be useful as an ingredient in a wide range of natural formulations.
Depending on the plant and extraction method, infused oils may contain various plant-derived aromatic compounds, pigments, phenolics and other oil-soluble constituents.
Ultrasound-assisted extraction provides another tool for getting those compounds from plant material into an oil carrier.
Instead of simply waiting for diffusion to do all the work, we're using physical energy to help the process along.
That's the fundamental idea behind ultrasonic-assisted herbal oil infusion.
The Boner's Botanicals Experiment
That's exactly what we're exploring here at Boner's Botanicals.
We're interested in practical ways to work with nature—and sometimes that means taking an old process and looking at it through a modern scientific lens.
Herbal infusion isn't new.
People have been combining plants and oils for generations.
What's interesting is discovering that modern ultrasonic technology gives us a way to investigate the physical processes behind that traditional practice.
The machine doesn't replace the plant.
It doesn't replace the oil.
And it doesn't replace the chemistry happening between them.
It simply gives us another tool for influencing the extraction process.
From Ancient Plants to Modern Physics
There's something pretty fascinating about that.
A dried herb may look completely still sitting inside a jar of oil.
But at the microscopic level, the situation can be very different.
Ultrasonic energy introduces rapidly changing pressure waves into the system.
Cavitation and related acoustic effects can generate mechanical forces.
Plant structures can be disrupted.
Contact between plant material and liquid can increase.
And compounds can move from the plant matrix into the surrounding oil.
All of this happens without us being able to see most of it.
Which means that when you look at an ultrasonic bath quietly humming away on a countertop, you're actually looking at a fairly energetic piece of physics.
Just happening on a scale too small for our eyes to see.
The Takeaway
So, can ultrasound accelerate herbal oil infusion?
The research says yes—ultrasound-assisted maceration has been demonstrated to accelerate the transfer of plant-derived compounds into oils under controlled experimental conditions.
But the scientifically honest answer comes with an asterisk.
Results depend on the plant, oil, equipment and processing conditions.
And while acoustic cavitation is a major mechanism behind ultrasound-assisted extraction, we shouldn't assume that every ultrasonic bath produces identical cavitation conditions inside every container or every oil.
That's exactly why experimentation is so interesting.
The science gives us a mechanism.
The published research gives us evidence.
And the experiment lets us see what happens in our own process.
That's where traditional herbal knowledge meets modern technology.
And that's where things get interesting.
A Note From Boner's Botanicals
This article discusses the science of ultrasound-assisted extraction and our own experimental process.
It is intended for educational purposes and is not a substitute for professional formulation, toxicology, regulatory or safety advice.
Not every herb is appropriate for every application, and extracting a plant compound more efficiently does not automatically make the resulting infusion safer or more beneficial.
Always research the specific plant, intended use, carrier oil and formulation before using an herbal infusion in a product intended for people.
Sources & Further Reading
1. Soares, V. P., et al. (2020).
"Ultrasound assisted maceration for improving the aromatization of extra-virgin olive oil with rosemary and basil."
Food Research International, 135, 109305.
DOI: 10.1016/j.foodres.2020.109305
This study is particularly relevant because researchers directly macerated rosemary and basil in extra-virgin olive oil using ultrasound and compared the results with conventional maceration.
2. Veillet, S., Tomao, V., & Chemat, F. (2010).
"Ultrasound assisted maceration: An original procedure for direct aromatisation of olive oil with basil."
Food Chemistry, 123(3), 905–911.
DOI: 10.1016/j.foodchem.2010.05.005
An earlier study demonstrating direct ultrasound-assisted aromatization of olive oil with basil and investigating volatile compounds transferred into the oil.
3. Hrebień-Filisińska, A. M., & Tokarczyk, G. (2023).
"The Use of Ultrasound-Assisted Maceration for the Extraction of Carnosic Acid and Carnosol from Sage (Salvia officinalis L.) Directly into Fish Oil."
Molecules, 28(16), 6094.
DOI: 10.3390/molecules28166094
Particularly relevant to herbal oil infusion because sage was extracted directly into oil using a 40-kHz ultrasonic bath.
4. Demesa, A. G., Saavala, S., Pöysä, M., & Koiranen, T. (2024).
"Overview and Toxicity Assessment of Ultrasound-Assisted Extraction of Natural Ingredients from Plants."
Foods, 13(19), 3066.
DOI: 10.3390/foods13193066
A recent review covering acoustic cavitation, plant-cell disruption, mass transfer, extraction efficiency and potential effects of excessive processing conditions.
5. Khalid, S., et al. (2024).
"Recent advances in the implementation of ultrasound technology for the extraction of essential oils from terrestrial plant materials: A comprehensive review."
Ultrasonics Sonochemistry, 107, 106914.
DOI: 10.1016/j.ultsonch.2024.106914
A broader review of ultrasound-assisted extraction and the physical mechanisms involved in extracting plant compounds.
Boner's Botanicals
Natural Products for Natural People.
We explore natural history, plants, wildlife and practical ways to work with nature—and sometimes that means putting a little modern science behind an old idea.
Exploring EMF Harmony
Our modern lives are surrounded by wireless technology, from smartphones and Wi-Fi routers to the many connected devices we use every day. For readers interested in learning more about electromagnetic fields (EMFs) and exploring products designed with that interest in mind, EMF Harmony offers a range of products focused on the EMF-conscious lifestyle.
Explore EMF Harmony and discover its product range.
Affiliate disclosure: This section contains an affiliate link. Boner’s Botanicals may earn a commission if you make a purchase through it, at no additional cost to you.
