Pasta comes in many shapes and sizes, which is part of its inherent delight. But all those irregular shapes tend to be inefficient when it comes to packaging. So what if you could buy your pasta of choice in a simple, compact 2D form and then watch it take on the desired final 3D shape as it cooks, thereby doubling the fun factor? Scientists at Carnegie-Mellon University (CMU) have figured out a simple mechanism to do just that, according to a new paper published in the journal Science Advances.

“We were inspired by flat-packed furniture and how it saved space, made storage easier, and reduced the carbon footprint associated with transportation,” said co-author Lining Yao, director of the Morphing Matter Lab at CMU’s School of Computer Science. “We decided to look at how the morphing matter technology we were developing in the lab could create flat-packed pastas that offered similar sustainability outcomes.” According to the team’s calculations, even if you pack macaroni pasta perfectly, you will still end up with as much as 67 percent of the volume being air. The ability to make flat pasta for shipping that takes on a specific 3D shape when cooked is one potential solution.

Yao and co-author Wen Wang, also at CMU, began experimenting with what they term “transformative appetite,” or shape-changing food, several years ago, inspired by their work with a bacterium that would shrink or expand in response to humidity—the same bacterium used to ferment soybeans to create natto, a popular Japanese breakfast dish that frankly smells a bit like aged cheese (and hence can be an acquired taste).

By 2017, Yao and Wang were producing edible 2D films of protein, cellulose, or starch. The films morphed into 3D shapes as they absorbed water such as pasta shapes (macaroni and rotini in this instance) and flowers. Their gelatin sheets have been compared to “edible origami” and also include spaghetti that spontaneously divides into smaller noodles when immersed in hot broth. Gelatin works well for this, because how much it expands is linked to its density, an easy variable to tweak to create tailored shapes.

There are two layers to the film, each made from a gelatin with a different density. The top layer is denser and hence absorbs more water than the bottom layer. So when the film is immersed in water, the top layer will curl over the bottom layer to form an arch. The researchers also found they could achieve greater control over when and how much the films would bend by topping the two-layer film with a 3D-printed strip of cellulose, which acts as a water barrier, thereby controlling how much water the top layer is exposed to. Voila! They had programmable edible gelatin films.

Not content to leave things in the lab, Wang and Yao approached Matthew Delisle, then-head chef for L’Espalier in Boston (since closed), about collaborating on the incorporation of their gelatin films into actual dishes. Delisle didn’t disappoint. He concocted a phytoplankton pasta salad, for instance, in which the pasta morphed from a flat disk into a saddle shape when hydrated, which he paired with heirloom tomatoes and wild sorrel. He paired the flowering pasta shapes with foraged mushrooms and fermented burgundy truffles, while the team’s helix noodles went well with squid, confit egg yolk, and white hoisin.

The most complicated dish involved transparent caviar cannoli, beginning as dry protein films in the shape of a square, which were then immersed in a bowl of water and caviar. As the films hydrated, they wrapped around the caviar, “filling” the final cannoli. Wang and Yao envision similar methods being used one day to make self-folding Chinese dumplings or self-wrapping tacos. Their co-authors even developed an online user interface, based on computational models of the various material transformations, so people could design their own edible morphing structures.

Nonetheless, the authors recognized that outside the lab (and experimental fine-dining establishments), edible materials are subject to unique constraints, both in terms of cost and safety requirements in manufacturing techniques and in nutritional requirements and culinary culture. In the case of pasta, for instance, traditional Italian pasta dough contains only semolina flour and water, which then swells as it cooks in boiling water. Adding things like cellulose strips would be neither practical nor desirable. So the researchers needed a simpler mechanism for inducing programmable shapes.

The solution: something Wang, Yao, and their co-authors term “groove-based transient morphing.” They found that stamping flat pasta sheets with different groove patterns enabled them to control the final pasta shape after cooking. According to the authors, the grooves increase how long it takes to cook that part of the pasta. So those areas expand less than the smooth areas, giving rise to many different shapes.

The team found that the pasta reached its maximum bending angle after about 12 minutes and retained this angle for around 20 minutes before it began to bend back. The researchers were able to produce simple helical and cone shapes, as well as more complex saddles and twists (the latter achieved by introducing double-sided grooves).

The basic principle should be applicable to any material that swells when immersed in water. The researchers demonstrated as much using the same groove technique to morph silicon (PDMS) sheets into different shapes, analogous to their pasta experiments. In addition to the benefits to sustainable packaging and shipping, the authors believe this approach could be useful in soft robotics and biomedical devices.

Another co-author, Ye Tao—formerly a visiting postdoc at the Morphing Matter Lab, now at Zhejiang University in China—actually took their flat-packed pasta on a hiking trip to test its robustness in a real-world setting. She found that the packed pasta took up less space in her backpack without getting damaged from all the jostling, and it cooked up just fine on a portable camp stove. Even better, “The morphed pasta mimicked the mouthfeel, taste, and appearance of traditional pasta,” she said.

DOI: Science Advances, 2021. 10.1126/sciadv.abf4098  (About DOIs).

Listing image by Morphing Matter Lab/CMU

https://arstechnica.com/?p=1762605