High Frequency Food: Better Cutting With Ultrasonics

You’re cutting yourself a single slice of cake. You grab a butter knife out of the drawer, hack off a moist wedge, and munch away to your mouth’s delight. The next day, you’re cutting forty slices of cake for the whole office. You grab a large chef’s knife, warm it with hot water, and cube out the sheet cake without causing too much trauma to the icing. Next week, you’re starting at your cousin’s bakery. You’re supposed to cut a few thousand slices of cake, week in, week out. You suspect your haggardly knifework won’t do.

In the home kitchen, any old knife will do the job when it comes to slicing cakes, pies, and pastries. When it comes to commercial kitchens, though, presentation is everything and perfection is the bare minimum. Thankfully, there’s a better grade of cutting tool out there—and it’s more high tech than you might think.

Shake It

Knives are very good at cutting food into distinct separate pieces. However, they have one major problem—food is sticky, and so are they. If you’ve ever cut through a cheesecake, you’ve seen this in action. Unless you’re very careful and deft with your slicing, the cake tends to grip the blade of the knife as it comes through. Try as you might, you’re almost always going to leave some marred edges unless you work very slowly.

While most home chefs and cafes can turn a blind eye to these sorts of things, that’s not the case in the processed food industry. For one thing, consumers expect each individually-packed morsel of food to be as cosmetically perfect as the last. For another, cutting processes have to be robust to work at speed. A human can compensate as they cut, freeing the blade from sticking and fettling the final product to hide their mistakes. Contrast that to a production line that slices ice cream bars from a sheet all day. All it takes is one stuck piece to completely mess up the production line and ruin the product.

This is where ultrasonic food processing comes in. Ultrasonic cutting blades exist for one primary reason—they enable the cutting of all kinds of different foods without sticking, squashing, or otherwise marring the food. These blades most commonly find themselves used in processed food production lines, where a bulk material must be cut into individual bars or slices for later preparation or packaging.

It’s quite something to watch these blades in action. Companies like Dukane and MeiShun have demo videos that show the uncanny ability of their products to slice through even the stickiest foods without issue. You can watch cheesecakes get evenly sectored into perfect triangular slices, or a soft brie cheese being sliced without any material being left on the blade. The technique works on drier materials too—it’s possible to cut perfectly nice slices of bread with less squishing and distortion using ultrasonic blades. Even complex cakes, like the vanilla slice, with layers of stiff pastry and smooth custard, can be cut into neat polygons with appropriate ultrasonic tooling.

The mechanism of action is well-understood. An ultrasonic cutting blade is formally known as a sonotrode, and is still sharpened to an edge to do its job. However, where it varies from a regular blade is that it does not use mere pressure to slice through the target material. Instead, transducers in the sonotrode vibrate it at an ultrasonic frequency—beyond the range of human hearing, typically from 20 kHz to 40 kHz. When the sonotrode comes into contact with the material, the high-frequency vibrations allow it to slice through the material without sticking to it. Since the entire blade is vibrating, it continues to not stick as it slides downwards, allowing for an exceptionally clean cut.

Generally, the ultrasonic sonotrode is paired with a motion platform to move the food precisely through the cutting process, and an actuator to perform the cutting action itself. However, there are also handheld ultrasonic knives that can be purchased for those looking to use the same technique manually.

The technique isn’t solely applied to the food industry. The same techniques work for many other difficult-to-cut materials, like rubber. The technique can also be applied to various textiles or plastic materials, too. In some cases, the sonotrode can generate enough heat as it cuts through the materials to melt and seal the edges of the material it’s cutting through.

If you’re simply looking to cut some cake at home, this technique might be a little overly advanced for you. At the same time, there’s nothing stopping you from rigging up some transducers with a blade and a DIY CNC platform seeing what you can achieve. If you want the most perfectly cubed sheet cake at your next office party, this might just be the technology you’re looking for.