On October 16th, the University of Tokyo (University of Tokyo) and Hiroshima University (Hiroshima University) selected sprouted vegetables as fresh samples for the possibility of plant cultivation in space, and simulated microgravity that can be tested on the earth. Announced that it investigated the effect of sprouted vegetables on freshness, and as a result, found that mass loss, which is a major phenomenon of freshness reduction, was significantly suppressed in a pseudo-microgravity environment compared to a normal gravity environment. ..

The result is a collaborative research team of Associate Professor Yoshio Makino of the Graduate School of Agricultural and Life Sciences, University of Tokyo, and Professor Yugeki, Graduate School of Medical Sciences, Hiroshima University. Details were published in the US online scientific journal “PLoS ONE”.

So far, research on the effects of space-specific environments such as microgravity and cosmic radiation on living organisms has been conducted at the Space Shuttle and the International Space Station (ISS). As a study on animals, many adverse effects such as degeneration of muscle bones and reduction of red blood cells have been observed.

In addition, for vegetables (plants), it has been observed that they continue to live even after harvesting and breathe while depleting the nutrients accumulated during cultivation, which causes wilting, discoloration, and loss of mass. (Findings on earth). Therefore, suppression of respiration has become an effective freshness maintenance method, and methods such as refrigeration, ethylene removal / nullification, and environmental gas composition control (low oxygen, high carbon dioxide level) have been put into practical use.

This means that the suppression of the important life activity of respiration is effective in maintaining the freshness of vegetables after harvesting, so the space environment that has a negative effect on life activity may be effective in maintaining the freshness. Is considered to be high. Therefore, the joint research team decided to investigate the effect of the pseudo-microgravity environment that can be created on the earth on the decrease in freshness of post-harvest vegetables.

In this study, the freshness of the harvested vegetables was compared with the samples placed in a pseudo-microgravity environment (μG) and placed in a normal gravity environment (1G). Pseudo-microgravity means that when an object is slowly rotated in the direction of 360 °, the average value of the gravitational acceleration applied to the object is approximated to about 1/1000 G on the earth. Also, “pseudo” is attached because it is different from microgravity in outer space.

And as samples, “mung bean sprouts” and “kaiware daikon” which are germinated vegetables (vegetables that have just sprouted), and “edamame” as fruits and vegetables (vegetables that eat fruits or seeds) were prepared. ..

And the pseudo-microgravity environment was created by the gravity control device “Gravite” manufactured by Space Bio Laboratories. The device is a device that can create a pseudo-microgravity environment of 1/1000 G, which is the same as the ISS, by rotating the sample 360 ​​° around two orthogonal axes and integrating the gravity vector on the time axis. On the contrary, it is possible to create a high gravity environment of 2G and 3G.

The vegetables were set in a gravity control device, their masses were measured over time, and comparisons were made with samples stored under normal gravity. The effect of gravity on mass retention was investigated, and as a result, in the case of germinated vegetables, the mass retention was significantly higher in the pseudo-microgravity environment than in normal gravity. It was confirmed that it is effective for maintaining freshness. On the other hand, in the case of edamame, the effect of gravity on the mass retention was not observed.

  • Gravite

    Freshness-preserving effect on germinated vegetables in a pseudo-microgravity environment using “Gravite” (Source: University of Tokyo / Hirodai joint press release PDF)

The mass loss of vegetables is mainly due to the transpiration that moves and releases the water it holds from the roots to the leaves. Since sprouted vegetables are items with roots and leaves, in a normal gravitational environment, the direction of water movement is sensed and the transpiration action is carried out smoothly, resulting in a significant mass loss. On the other hand, in a pseudo-microgravity environment, it is considered that smooth transpiration is hindered because the direction of water movement cannot be detected, and as a result, mass reduction is suppressed.

However, in the case of edamame, which is a fruit vegetable, it does not have roots and leaves, and because it is a mass loss due to the release of water in a natural form that has nothing to do with gravity perception, the effect of gravity was not recognized. .. From these results, it was proved based on experimental data that the pseudo-microgravity environment is effective in maintaining the freshness of sprouted vegetables.

In space development, plant cultivation research has been carried out for many years, but it goes without saying that the fresh produce that is the harvest is a valuable food source in outer space. Therefore, it is important to secure food resources to keep the freshness as long as possible. The results of this research are said to be able to contribute to space development research support as an effective conservation method for food resources in outer space.

Furthermore, it is said that there is a social significance of discovering a new freshness preservation method. As for the method of maintaining the freshness of vegetables, refrigeration, ethylene removal / nullification, and control of expected environmental composition have been put into practical use, but since there have been no reports in the past regarding the method of maintaining the freshness of gravity, this time. The novelty of the research results is supported.

In the future, the joint research team hopes to continue its activities toward collaboration with researchers on plant cultivation in outer space and the development of a new style of freshness preservation device focusing on gravity control.

  • Gravite

    Mechanism of mass retention of sprouted vegetables in a pseudo-microgravity environment (Source: University of Tokyo / Hirodai Joint Press Release PDF)