Fermented foods are enjoyed around the world for their potent, often salty, spicy and umami flavours. This makes them particularly attractive to astronauts, who report that their palates can get dulled in space. Although many dishes have been eaten and prepared on the International Space Station (ISS), nothing has ever been fermented there. Indeed, given that microgravity and the high levels of radiation in space might disrupt the microbial interactions needed to make this process happen, it has always been unclear if fermentation was even possible in space.
Maggie Coblentz at the Massachusetts Institute of Technology and Joshua Evans at the Technical University of Denmark have now proved that fermentation is possible by creating miso, a cherished Japanese condiment, in space. The researchers first created a ready-to-ferment miso mixture using cooked soyabeans, salt and rice that had previously been fermented with a fungus called Aspergillus oryzae. The soon-to-be miso was split into three containers and frozen. One was kept in Denmark, one was shipped to Massachusetts and one was sent to Houston, Texas to be loaded onto a spacecraft bound for the space station. All the mixtures were allowed to ferment for several weeks.
When the miso was brought back from the ISS to Earth for analysis, the researchers were able to identify all of the bacteria, amino acids and volatile compounds that are normally found in the Japanese condiment. Taste tests demonstrated that the flavour was similar and that it was liked just as much as the Danish and Massachusetts miso samples. Even so, it was different enough for Ms Colbentz and Dr Evans to call it “space miso.” The results are reported this week in iScience, a journal.
The space miso had a more potent sweet flavour than the regular kind, which came from the high levels of phenylacetic acid methyl ester, a component also found in honey, brandy and some wines. It also had stronger cheese-like flavours that were probably the result of it having higher concentrations of 2-methyl-butanoic acid. Why these compounds were found in higher concentrations is not yet confirmed, but it is probably due to the microgravity on the station. In normal circumstances on Earth, gas bubbles produced by the microbes during fermentation would just rise upwards to the surface. Not so in space. In microgravity, the bubbles would have travelled in all sorts of directions and this probably affected the growth of the microbes by altering the way in which vital gases, like oxygen, were dispersed.
Now that fermentation has been shown to be possible, the potential is there to make other foods in space—hot sauce or, perhaps more important, beer. ■
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