An experiment on board the International Space Station (ISS) has produced miso paste in what is thought to be the first deliberate food fermentation ever conducted off Earth.
Miso is an umami-rich paste from Japan made from fermented soya beans, with origins stretching back thousands of years. at the Technical University of Denmark and his colleagues say it could 鈥渟atisfy astronauts鈥� need for flavour鈥� on long space missions.
鈥淲e were keen to investigate whether the space environment might shape fermentation processes, its microbial ecology and flavour chemistry, in specific ways,鈥� says Evans. 鈥淭he space environment presents some fairly unique conditions 鈥� increased radiation and microgravity, in particular 鈥� which fermentation processes had not yet been exposed to.鈥�
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To test the feasibility of producing fermented foods in space, the researchers prepared a small container of cooked soya beans with koji, a fermented rice product containing the fungus Aspergillus oryzae, and salt. This fungus and a variety of bacteria transform the soya beans with their metabolism to turn it into miso.
The miso mixture was split into three portions and kept frozen until the start of the 30-day experiment. One portion was sent to the ISS on a SpaceX rocket in March 2020, while the other two were fermented in Cambridge, Massachusetts, and in Copenhagen, Denmark.
While on the ISS, the miso was kept in a box with sensors that measured temperature, relative humidity, pressure, light and radiation. It was brought back to Earth after 30 days in orbit.
Evans and his colleagues tasted the miso themselves. 鈥淭hese misos looked like miso, smelled like miso and the recipe was a tried and tested one, so we didn鈥檛 feel much cause for concern,鈥� says Evans. 鈥淪o though we hadn鈥檛 done any analysis on them at that point, we felt comfortable tasting them as our own guinea pigs, participating in a long and venerable tradition of scientists experimenting first on themselves.鈥�
The space miso tasted different from the two earthbound samples, he says. 鈥淚t was more pungent than the other two, with more nutty and roasted aromas and more umami taste. It even looked different 鈥� it was darker in colour. All of these characteristics suggest that the fermentation process for the space miso went faster than for the earthbound controls.鈥�
The researchers also carried out genomic analysis to identify the microbes present in the samples. The bacterium Bacillus velezensis, which has been found in other fermented foods and is considered safe to eat, was only detected in the space miso.
at the University of Queensland, Australia, says the study provides a proof of concept for making fermented foods in space. 鈥淭hey convincingly show that the space miso is a safe-to-eat 鈥榬eal miso鈥�, albeit with a distinct space 鈥榯erroir鈥�,鈥� he says. 鈥淭erroir鈥� refers to the influence of a specific environment on the flavour of wine or other products made using microbes.
鈥淚t is interesting to consider the possibilities of future astronauts on long missions growing their own food in circular systems that recycle nutrients and water, and how fermentation might help improve its nutrition and taste,鈥� he says.
One possible reason for differences in space-based fermentation is the lack of gravity, which normally lets carbon dioxide leave the system as bubbles, and forces denser particulates and microbial cell mass to settle to the bottom of fermenters. Neither of these would happen in the low or zero-gravity setting of space and it isn鈥檛 clear how this would affect the fermentation speed, quality or safety, says Schulz.
bioRxiv
