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Miso Fermented On The International Space Station Is Out Of This World

For the first time, fermentation has been achieved in space. Miso made aboard the International Space Station (ISS) aged faster than the controls kept on Earth and contained more fungal mutations.

Miso is a Japanese condiment made by fermenting cooked soybeans, kōji (a starter culture containing the fungus Aspergillus oryzae) and salt. Similar to other fermented foods like sourdough, misos also contain microbes that originate from the environment in which they're made, and the people who make them. As such, misos can be said to have a terroir, a term originating in winemaking that can be likened to a 'taste of a place', or in this case, a 'taste of space'.

Orbiting about 400km above the Earth, the ISS's environment is unique thanks to its microgravity and increased radiation exposure, as well as by the multinational astronauts that visit it, bringing unique microbiomes with them. While fermented foods have been taken to the ISS before, fermentation hasn't been done in space until now.

An international team of researchers prepared a miso precursor in Copenhagen, Denmark and divided it into three portions. One sample stayed there and the other two were placed in environmental sensing boxes, which measured temperature, relative humidity, pressure, off-gassing, light and radiation and sent to Cambridge, US, and the ISS. After 30 days in low Earth orbit, the space miso was returned and all three pastes underwent metagenomic, metabolomic and sensory analysis.

On average, the space-aged miso experienced temperatures roughly 13 and 16°C higher than the Cambridge and Copenhagen misos respectively, accelerating its fermentation. The mean concentration of aroma compounds was highest in the ISS miso, which had levels of esters up to 30 times higher and pyrazines six times higher than its earthly counterparts. The higher pyrazine content, which imparted a roasted, nutty flavour, likely resulted from Maillard reactions which are accelerated by heat. While all three misos featured glutamate, known for imparting an umami taste, the ISS miso showed higher levels of asparagine and lower levels of histidine, both indicators of maturity.

Although all three miso samples contained different proportions of microbe species, pathogenic species were found only in the top portions of the misos. Traditionally, the top layer of miso is discarded before eating, as was done for these samples prior to taste tests. Genetic analysis found a greater number of Aspergillus oryzae variants in the space paste – likely due to the increased radiation levels on board the ISS.

In double-blind taste tests, all three misos were enjoyable, but the Copenhagen miso was the favourite. The earth-fermented misos, however, were associated with a 'beany' taste associated with underfermentation.

Miso was chosen for this space mission for several reasons. Practically speaking, a paste is less likely to leak and compromise either the experiment or sensitive ISS equipment. On top of this, with the sensory-dulling effects of space, strongly flavoured foods, especially those rich in umami, are particularly valuable to combat the 'flavour boredom' that plagues astronauts on long missions.

Miso In Microgravity: Fermented Flavor Takes Off Aboard The International Space Station

Miso, the beloved Japanese paste made by fermenting cooked soybeans and salt, is known for its rich umami flavor and versatility in the kitchen. But what happens when you take this centuries-old culinary tradition and send it into orbit?

That's the question a team of researchers sought to answer in a new study published  in the journal iScience. Their goal? To test whether fermentation, a process driven by live microbes, could succeed in the harsh environment of space—and whether the resulting food would still be edible or even enjoyable.

"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," co-lead author Joshua D. Evans of the Technical University of Denmark said in a recent statement. "We wanted to explore the effects of these conditions."

Making Miso on the ISS

In March 2020, the team sent a small container of "miso-to-be" to the International Space Station (ISS), where it remained for 30 days to ferment. Two identical batches were kept on Earth—one in Cambridge, Massachusetts, and one in Copenhagen, Denmark—as controls. To closely monitor the process, each batch was housed in a specially designed box that tracked temperature, humidity, pressure, and radiation levels.

After the ISS miso returned to Earth, researchers analyzed its microbial communities, amino acid composition, and, of course, flavor. They found that despite the challenges of space, the miso fermented successfully. Interestingly, the bacterial makeup of the space miso differed from its Earth-bound counterparts, likely due to the effects of microgravity and radiation.

"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," co-lead author Maggie Coblentz of the Massachusetts Institute of Technology noted. "While the ISS is often seen as a sterile environment, our research shows that microbes and non-human life have agency in space."

As for the taste, researchers reported that all three samples had the classic salty, umami-rich profile expected from miso. But the ISS miso stood out with a slightly more roasted, nutty flavor—an intriguing variation that may reflect its time in orbit.

Miso in Space: Flavor, Well-Being, and Equity

Beyond proving that miso can ferment in microgravity, the study opens doors to new possibilities in space food systems. For astronauts on long-duration missions, fermented foods like miso could offer not just nutrition but comfort, variety, and a connection to Earthly traditions.

"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 said. "It could enhance astronaut well-being and performance, especially on future long-term space missions."

However, the researchers also see broader meaning in the work. Coblentz pointed out that using food as a scientific and cultural tool can spark meaningful conversations about who participates in space exploration—and how we design systems that reflect diverse human experiences.

"We've used something as fundamental as food as a starting point to spark conversations about social structures in space and the value of domestic roles within scientific and engineering fields," said Coblentz. "The way we design systems in space sends a powerful message about who belongs there, who is invited, and how those people will experience space."

In other words, a jar of space-fermented miso may be small, but it carries significant implications for the future of food, science, and humanity among the stars.

Kenna Hughes-Castleberry is a freelance science journalist and staff writer at The Debrief. Follow and connect with her on BlueSky or contact her via email at kenna@thedebrief.Org

Tracing Miso Soup's Roots: From Ancient Japan To Modern Comfort

Miso soup is not just comforting, it's also nutritious.

Being fermented soybean-based, it packs essential nutrients such as vitamins B and E, calcium, iron, and protein.

The fermentation process also promotes gut health by adding healthy probiotics into the gut.

Plus, low on calories but high on flavor, it makes a perfect addition to any health and wellness-focused diet plan.

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