“Who hasn’t dreamt of coming home after a long day and simply pressing a few buttons to get a hot, home-cooked 3D-printed meal, courtesy of one’s digital personal chef? It might make microwaves and conventional frozen TV dinners obsolete. Engineers at Columbia University are trying to make that fantasy a reality, and they’ve now figured out how to simultaneously 3D-print and cook layers of pureed chicken, according to a recent paper published in the journal npj Science of Food. Sure, it’s not on the same level as the Star Trek replicator, which could synthesize complete meals on demand, but it’s a start.
Co-author Hob Lipson runs the Creative Machines Lab at Columbia University, where the research was conducted. His team first introduced 3D printing of food items back in 2007, using the Fab@Home personal fabrication system to create multimaterial edible 3D objects with cake frosting, chocolate, processed cheese, and peanut butter. However, commercial appliances capable of simultaneously printing and cooking food layers don’t exist yet. There have been some studies investigating how to cook food using lasers, and Lipson’s team thought this might be a promising avenue to explore further.
“We noted that, while printers can produce ingredients to a millimeter-precision, there is no heating method with this same degree of resolution,” said co-author Jonathan Blutinger. “Cooking is essential for nutrition, flavor, and texture development in many foods, and we wondered if we could develop a method with lasers to precisely control these attributes.” The researchers used a blue diode laser (5-10 W) as the primary heating source but also experimented with lasers in the near- and mid-infrared for comparison, as well as a conventional toaster oven.
The scientists purchased raw chicken breast from a local convenience store and then pureed it in a food processor to get a smooth, uniform consistency. They removed any tendons and refrigerated the samples before repackaging them into 3D-printing syringe barrels to avoid clogging. The cooking apparatus used a high-powered diode laser, a set of mirror galvanometers (devices that detect electrical current by deflecting light beams), a fixture for custom 3D printing, laser shielding, and a removable tray on which to cook the 3D-printed chicken.
“During initial laser cooking, our laser diode was mounted in the 3D-printed fixture, but as the experiments progressed, we transitioned to a setup where the laser was vertically mounted to the head of the extrusion mechanism,” the authors wrote. “This setup allowed us to print and cook ingredients on the same machine.” They also experimented with cooking the printed chicken after sealing it in plastic packaging.
The results? The laser-cooked chicken retained twice as much moisture as conventionally cooked chicken, and it shrank half as much while still retaining similar flavors. But different types of lasers produced different results. The blue laser proved ideal for cooking the chicken internally, beneath the surface, while the infrared lasers were better at surface-level browning and broiling. As for the chicken in plastic packaging, the blue laser did achieve slight browning, but the near-infrared laser was more efficient at browning the chicken through the packaging. The team was even able to brown the surface of the packaged chicken in a pattern reminiscent of grill marks.
“Millimeter-scale precision allows printing and cooking a burger that has a level of done-ness varying from rare to well-done in a lace, checkerboard, gradient, or other custom pattern,” the authors wrote. “Heat from a laser can also cook and brown foods within a sealed package… [which] could significantly increase their shelf life by reducing their microbial contamination, and has great commercial applications for packaged to-go meals at the grocery store, for example.”
To make sure the 3D-printed chicken still appealed to the human palate, the team served samples of both 3D-printed laser cooked and conventionally cooked chicken to two taste testers. It’s not a significant sample size, but both taste testers preferred the laser-cooked chicken over the conventionally cooked chicken, mostly because it was less dry and rubbery and had a more pleasing texture.
One tester was even able to identify which sample was the laser-cooked chicken and did note a slight metallic taste from the laser heating. “Ever go to the dentist and get fillings done?” the tester told the researchers. “They have a laser they use to seal the fillings and you get that smell—a little bit of an industry odor, a sharpness that you don’t get with normal chicken.”
This was essentially a proof of principle, only involving the use of chicken, but the authors are confident that the method can be extended to other model food systems, including other animal meats and grains. In fact, “Laser heating of grain-based substrates that more readily absorb water should accelerate moisture loss and browning during cooking as well,” they wrote.
For future research, the team hopes to investigate ways to use multiple laser wavelengths to achieve both internal and external cooking simultaneously. They would also like to figure out how to reduce cross-contamination between cooked and raw printed layers and how to develop software to enable users to tailor their own 3D-printed meals in the future.
“What we still don’t have is what we call ‘Food CAD,’ sort of the Photoshop of food,” said Lipson. “We need a high-level software that enables people who are not programmers or software developers to design the foods they want. And then we need a place where people can share digital recipes, like we share music.”
DOI: npj Science of Food, 2021. 10.1038/s41538-021-00107-1 (About DOIs).”