Astronauts often notice that their enjoyment of food decreases during their stay in space. Food that is extremely tasty on Earth can become bland and unappealing in orbit.

Although dietary plans are carefully crafted for space missions, astronauts often struggle with inadequate food intake that fails to meet their energy needs. This phenomenon raises the question of what exactly happens to our senses in space conditions.

To understand these changes, research has been conducted on Earth using virtual reality (VR) and simulated spacecraft to discover how the space environment affects the sense of smell and the experience of food.

Research has shown that some smells seem more intense in space-like conditions, suggesting that previous theories about the impact of zero gravity on the body have not fully explained the phenomenon. The research results, published in the International Journal of Food Science and Technology, could be key to developing future space menus.

Food and its consumption are complex processes involving many senses such as sight, smell, taste, hearing, and touch.

For a full experience of food's taste – for example, when biting into an apple – a combination of senses is needed: taste (sweet, sour), smell (a complex blend of apple aromas), texture (crispness), color (green, red), and touch (firmness). If any of these senses is diminished, the enjoyment of food is not the same.

The experience of food in space is very different from what we are used to on Earth.

One possible explanation for the altered taste experience in space is the lack of gravity. Without gravity, bodily fluids do not accumulate in the lower part of the body but are directed towards the head, which can lead to a feeling similar to a stuffy nose. If you have ever had a cold, you know how difficult it can be to enjoy food without a normal sense of smell.

However, there may be other reasons for these changes.

The environment plays a significant role in the food experience. In space, the environment is unfamiliar and constantly monotonous. Could such circumstances change our perception of food?

Context significantly contributes to the dining experience. Research has shown that eating the same meal in different environments can lead to different impressions of that meal. Imagine enjoying a sandwich at a picnic in a beautiful park versus quickly eating the same sandwich at a work desk.

Spacecraft are enclosed and limited spaces, hermetically sealed containers with an environment filled with wires and equipment, without a clear boundary between work and personal space. Imagine a quarantine situation like the one during the pandemic, lasting several years, with limited food and essential supplies (and a constantly stuffy nose).

One taste testing study compared meals in airplanes in three different environments: a classic sensory lab (quiet, enclosed or semi-enclosed booths – like voting booths), a semi-realistic airplane environment simulated in a lab using airplane furniture, and an actual flight.

Passengers in the simulated airplane environment enjoyed their meals almost as much as passengers on real flights. (Both were less satisfied compared to those in the lab environment.) These results suggest that the airplane environment significantly affects food enjoyment.

Simulating Space on Earth
Researching human reactions in space is extremely challenging. Space missions usually involve only six or seven crew members, significantly limiting the sample size for experiments and the predictive power of the results.

Moreover, in food research, each person has unique sensory experiences and reactions, making it difficult to understand how different people perceive smells in space, let alone food aromas.

Therefore, we decided to reconstruct space conditions on Earth. Using VR, we simulated the environment of the International Space Station.

Using VR allowed us to collect data on participants' reactions to food stimuli "in the moment," instead of waiting for them to remove the headset and ask them afterward. VR is an extremely important tool for astronaut training due to its ability to create a realistic sense of presence, which is crucial for studying life on a spacecraft.

Our study is the first to include a significant sample (54 people) to record variations in personal experiences with smells and tastes in simulated isolated environments.

In our study, we compared everyday smells. Some smells were perceived differently in the virtual environment of the International Space Station compared to the environment in lab booths.

Molecular Properties of Smells
Smells are complex mixtures of molecules with unique chemical structures that influence interaction with olfactory receptors in the nose to create specific scents.

Our study suggests that only certain smell compounds are perceived differently in space-like environments. We found that molecules with sweet smells are often perceived more intensely.

Vanilla and almond, which contain the sweet compound benzaldehyde, smelled stronger in our VR spacecraft than in the control environment. On the other hand, there was no difference in the perception of lemon aroma.

These findings could be useful in designing space meals. For example, sweet aromas could be used as flavor enhancers or additives to highlight other flavors and add depth.

Understanding how these smell compounds interrelate and finding optimal concentrations is crucial. It's also important to note that no single aroma suits all tastes.

Implications on Earth
Better understanding how smell is perceived in space-like conditions could drive the development of personalized diets based on the unique sensory experiences and preferences of each astronaut. By adjusting food aromas, we could encourage space travelers not only to consume more food but also to enjoy it more.

These insights could also help people on Earth living in isolated or confined conditions, such as residents of nursing homes, individuals on military missions, and submarine crews.

Original:
Julia Low
Senior Lecturer in Nutrition and Food (Sensory Science), RMIT University
Grace Loke Mei Ing
PhD in Food Science, RMIT University
Ian Peake
Digital Solutions Architect, RMIT University
Jayani Chandrapala
Associate Professor, RMIT University
Lisa Newman
Lecturer in Nutrition at RMIT University