A spoonful of miso, rich with umami and history, made its way around the International Space Station. There, 250 miles above Earth, the centuries-old traditional Japanese food encountered the alien physics of space. And it thrived.

In a recent study, scientists announced that they successfully fermented miso—a Japanese paste made from soybeans and salt—in orbit. The paste spent 30 days on the International Space Station (ISS) in March 2020, returning to Earth as a full-fledged, microbially matured condiment.

It smelled and tasted somewhat like Earth-made miso, but with a twist. “It had a slightly nuttier, more roasted flavor,” said the researchers. In that twist, there could be important information about how astronauts’ food will taste in the future.

Food in space

The project began with both curiosity and necessity. As astronauts gear up for longer missions—think Moon bases and journeys to Mars—they will need diverse, nutritious, and satisfying foods. If fermentation—one of humanity’s oldest methods of preserving and enhancing food—can unfold even in the microgravity-riddled environment of space, it could very useful.

Of course, there’s also the curiosity of seeing how things ferment in space.

“There are some features of the space environment in low earth orbit—in particular microgravity and increased radiation—that could have impacts on how microbes grow and metabolize and thus how fermentation works,” says co-lead author Joshua D. Evans of Technical University of Denmark. “We wanted to explore the effects of these conditions.” 

So Evans and his colleagues sent a small jar of “miso-to-be” to orbit. It was accompanied by environmental sensors that tracked humidity, temperature, pressure, and radiation. Two control miso batches stayed grounded—one in Cambridge, Massachusetts, the other in Copenhagen, Denmark.

After its 30-day orbit, the ISS miso came home. Then, the food detective work began.

Microbes in Microgravity

Fermentation relies on a teeming legion of bacteria and fungi. Each microscopic microbe works to transform the substrate into food. But it’s not at all clear that they’d behave the same in space.

The microgravity and increased radiation alter how microbes grow, interact, and metabolize. When the space miso was brought home, it was investigated using metagenomic sequencing, metabolomic analysis, and sensory testing. Metagenomic sequencing identifies all the microbes in a sample by reading their DNA; metabolomic analysis measures the chemical compounds they produce during fermentation; and sensory testing involves humans tasting the food to judge its flavor, aroma, and texture.

It was, without a doubt, the familiar taste of miso. Same aroma, same texture. However, the ISS miso had more of a roasted, nutty flavor than the Earth misos. The in-depth analysis showed a distinct microbial fingerprint—a space terroir. This uniqueness is shaped by radiation, microgravity, and perhaps even the cabin’s unique microbial milieu.

“Fermentation [on the ISS] illustrates how a living system at the microbial scale can thrive through the diversity of its microbial community, emphasizing the potential for life to exist in space,” says co-lead author Maggie Coblentz of the Massachusetts Institute of Technology.

“While the ISS is often seen as a sterile environment, our research shows that microbes and non-human life have agency in space, raising significant bioethical questions about removing plants and microbes from their home planet and introducing them to extraterrestrial environments.”

Beyond the jar

This isn’t the first time fermented foods have entered orbit. Past missions have brought along kimchi and wine—though those were pre-fermented, cooked into stasis before launch. These gestures often served cultural pride or marketing stunts. This time was different.

The researchers weren’t interested in sending food to space, but in making it there—alive, changing, reacting. That distinction matters.

“By bringing together microbiology, flavor chemistry, sensory science, and larger social and cultural considerations, our study opens up new directions to explore how life changes when it travels to new environments like space,” Evans says.

“It could enhance astronaut well-being and performance, especially on future long-term space missions. More broadly, it could invite new forms of culinary expression, expanding and diversifying culinary and cultural representation in space exploration as the field grows.”

It’s easy to think of the future of space food as engineered fuel—efficient, sterile, tasteless. But miso in orbit suggests another future is possible: one where flavor and fermentation join the astronaut toolkit.

Ultimately, food isn’t just calories. It’s memory, culture, and comfort. For astronauts, it can be a reminder of Earth and a tether to home. It could help them be happier an even perform better, the researchers conclude.

“Fermentation in space raises questions for health research—not only physical health and productivity but also mental and emotional health and well-being and their connections to sensory satiety, pleasure, and enjoyment. Fermentation in space can offer astronauts improved nourishment and gut health, which is linked to behavior and cognitive performance.”

“Fermented foods may help alleviate sensory-specific satiety, or flavor boredom, which can arise from astronauts’ current predetermined diets and negatively impact their well-being and nutrient intake.”

The study was published in iScience.