Course:FNH200/Projects/2021/Space Foods
Introduction
When people think about food in space, they probably imagine items like freeze-dried ice cream. With the development of food preservation technology, foods on space missions are no longer boring or repetitive. In fact, there are four main preservation techniques, all of which apply to different foods. Like all preservation methods, these techniques have qualitative and nutritional effects on food products. In this project, we explore the historical and current space food preservation methods, along with their impact on food.
Space Food Preservation
What Are the Common Space Food Preservation Methods?
Freeze Dehydration
Most of the food on the Apollo missions run from 1963 to 1975 was preserved through the process called freeze dehydration. Freeze dried foods were first used by NASA on their Mercury 9 mission in 1963[1]. This technique allows for less vitamin loss and greater flavour retention of a product than any other food drying method. It is a very famous space food preservation technique because it increases the shelf life of food products and reduces their weight. The process involves preparing the food to a ready to eat stage, followed by freezing, then placing the food in a freeze dryer vacuum chamber (where the food is heated to remove all water) and finally removing the moisture through sublimation (final moisture content < 3%)[2]. The food is also immediately packaged after being removed from the freeze dryer to prevent the reabsorption of moisture. By using this technique, natural oils are retained and foods preserved in this manner can be kept at room temperature for long periods of time. All this freeze-dried food can then be consumed on the space shuttle and the ISS after the addition of water. A popular example of freeze dehydrated food is shrimp cocktail.
Intermediate-Moisture Food
Another food preservation technique used for space foods. It involves reducing the moisture of food and thus lowering the water activity in order to increase the foods’ shelf life. They have water activities of 0.6 to 0.84 and moisture content ranging from around 15% to 40%[2]. They are shelf-stable, are edible without rehydration and are below the minimum water activity for most bacteria to form. They are commonly bite-sized foods like beef squares and are first cooked, followed by being pressed into their shape and finally packaged.
Freezing (Frozen Foods)
Frozen foods are another way in which space foods are prepared and preserved. Although these foods have not been used since the Skylab mission, they have been planned for by the ISS[2]. One of the reasons why they had not been used frequently since the Skylab mission is because there was no freezer at the ISS and so the frozen foods would spoil as they are not very shelf stable. The food is first cooked, then placed into a frozen food container made of crystallized polyethylene terephthalate (CPET), sealed and finally frozen. Prior to eating, these cans are placed in a serving tray or a food warmer and were warmed from approximately -23 C to 65 C in a span of 2 hours[2]. Frozen foods however provide a significant menu quality improvement for the astronauts and at the ISS Assembly, it was decided that 50% of the food on upcoming space crafts is planned to be frozen as technology improvements have resulted in new ways to keep these foods frozen at the ISS[2].
Thermostabilized Food
Thermostabilized food is another popular space food preservation method. It was initially part of the contingency food supply on the Apollo space missions[2]. The foods were packaged in flexible metal tubes which were designed to provide nutrients to astronauts wearing a pressurized space suit incase of emergency operations. Nowadays, these foods are first cooked and then inserted into pouches that are made out of polypropylene, laminated polyester and aluminium foil. The pouches are then induction sealed and retorted to commercial sterility. These thermostablized pouches are similar to foods in retort pouches on Earth. Presently, eight different types of foods are thermostabilized in pouches in the ISS shuttle program[2].
How Long Does Space Food Last?
The shelf life of space food is stated to be only 1.5 years[3]. However, recent research has pointed out that the current prepackaged food system might not be able to pass the requirements in terms of nutrition, safety, and acceptability[3].
What Are the Nutritional Problems? What starts to break down?
During processing and storage life of processed foods, nutrient changes include isomerization of vitamins or vitamin precursors, changes in bioavailability of amino acids and nutrient as of structure breakdown, and oxidation of several vitamins and amino acids[3]. It has been studied that the storage of canned fruits and vegetables for 2 years at 80°C led to the losses in ascorbic acid, riboflavin, and thiamin up to 58%, while the same products stored at 10°C was indicated to have the losses as high as 38%[3]. Several key nutrients in the space food can later be degraded or lost such as vitamin A, vitamin C, folic acid and thiamin due to the gradual change based on its natural breakdown or due to space radiation beyond low-Earth orbit[3]. High radiation will decrease nutritional stability which requires ideal cold storage. The consideration of environment changes, processing equipment, and procedures can affect and determine safety for consumption and prevent possible food borne illnesses[4]. It is important to obtain the nutritious characteristic of space food because microgravity causes astronauts to lose calcium, nitrogen, and phosphorus[3]. Besides, appealing characteristic is essential as well since the additional burden from the reduced appetite due to combined effects of fluid shifts, pressure changes, nausea and workload can result in lower caloric and nutrient intake, which at the end contribute to greater health risks[4].
Qualitative Aspects of Space Foods Over Time
How Does Space Food Preservation Affect the Qualitative Aspects of the Food?
When it comes to taste, astronauts often find that foods aren’t as intense due to the difference in gravity[5]. This is because in space, the lack of gravity causes the body’s sinuses to fill with fluids[5], and thus reducing their ability to detect aroma molecules. Yet, the body is eventually able to accustom itself to this change and their taste goes back to normal[5]. Once this happens, astronauts are left with very similar meals for what can be lengthy trips[5]. Therefore, it is important that they are sent to space with flavourful foods that will sustain them for their mission[5].
How Does This Compare to Older Techniques?
The development of space foods to retain the textural and aromatic components of Earth food have been a lengthy process. In the past, astronauts ate foods that were conserved by placing them in metal tubes[6]. These tubes were able to prevent the food from spoiling, however, the texture of the food was limited to what was easy to place in and eat from a tube[6]. Metals are often used to preserve or package food because of their natural ability to discourage the growth of bacteria[7]. Another technique was to compact the food (i.e. by applying pressure to the food) into an energy-dense cube[6]. While these cubes were able to conserve the flavour of the original food, they were a strange texture, and therefore were often not eaten during trips[6]. One of the most recent developments is the use of cans and pouches to store food[6]. The use of these techniques allowed for the food to be kept at room temperature for long periods of time due to the sterility of the storage process[6]. The main concern for the present and the future will be in developing techniques that will be able to sustain food for much longer voyages while maintaining their original flavour and vitamins[6].
Space Food Characteristics
Foods Served in Space
Numerous challenges in space require certain criteria for foods to be selected and served there. First of all, foods have to be compacted and lightweight since space is limited on board and sending foods into orbit is extremely costly[8]. Nutrition requirement is one of the strict considerations of space food to ensure healthy diets and sufficient vitamins and caloric energy for astronauts, depending on their weight, gender, and specific needs[8]. Besides, foods need to be tasty because microgravity reduces astronauts' sense of taste[8]. Space food has to be sticky or wet because crumbs and particles will float around freely due to zero gravity and possibly get stuck in the equipment[8]. The conditions in space also demand foods to be processed or pasteurized, ensuring them to be kept for at least entire mission journey[8].
Several common types of foods that cannot be served in space are bread, soda or pop, fish, and chips. For a long time, bread has been banned because it often lacks structure, leaves crumbs, and has short shelf life to be kept in space[9], and the limitation for astronauts is tortillas which can last for an entire year[10]. Carbonated beverages like Coke and Sprite act differently in space than on Earth, that is, carbon dioxide bubbles instead of being released as gas for an effervescent pop, remain within the liquid[9]. For that reason, astronauts can experience digestive issues if consuming soda or pop. For the case of fish, this food type cannot be stored for a long time without turning bad, especially when there is no effective refrigerator or freezer for food storage in space, thus freeze-dried shrimp is the exception[11]. Chips and junks do not provide sufficient nutrition for the astronauts to keep up with the microgravity environment[11]. Instead, they can consider fruits and nuts for their snack time.
Different Forms of Food in Space
Food in space falls into six different categories based on the conservation method. Astronauts consume food that is either fresh, in its natural form, dried, irradiated, rehydratable, or thermostabilized. Foods in natural form are packed as-is in flexible pouches, they require no preparation prior to eating[12]. Foods like nuts, tortillas, granola bars, cookies, brownies, and fruits are considered natural form foods by NASA[12]. Fresh foods like fruits and vegetables can be delivered occasionally to the space station by cargo vessels[12]. Examples of dried foods include dried fruit and dried beef. Irradiated foods like chicken breasts and smoked turkey go through ionizing radiation to destroy harmful microorganisms[12]. Foods that fall into the thermostabilized category have been heat-treated, for example, tuna salads and vanilla flan. Some foods spoil from bacteria that live in wet environments. To prevent food items from spoiling and to conserve weight, some foods in space are rehydratable. Rehydratable foods are foods whose water content has been extracted by food scientists, resulting in very dry foods[12]. This is done because the bacteria that decomposes foods struggle to survive in dry environments[12]. Common examples of rehydratable foods in space include spinach and juices/beverages. The rehydratable foods must be combined with water before eating, all foods which require preparation have labels with instructions.
Nutritional Aspects of Space Foods (Carbohydrates, Fats, Proteins)
It is very important for astronauts to maintain a healthy balanced diet. Food scientists and nutritionists work closely to prepare space foods with a balanced supply of vitamins and minerals, while making sure the foods can be preserved for the length of the mission. Things like limited water, storage, and food preparation necessities (adding water, heat) narrows the crew’s choice of food to shelf-stable, single-serving food items[13]. The leading cause of death and mission failures in the past have been due to weaknesses in the space food system, such as nutrient deficiencies, insufficient calories and under consumption, poor preservation, or nutrient toxicities[13]. Fortunately, modern science and nutrition has progressed to prevent such issues on space missions. Let's take a look at food major components and their intake in space:
Carbohydrates: Carbohydrate requirements in space are said to be similar to those on earth. There are very few studies done on the effects of microgravity on the metabolism of dietary carbohydrate, and the studies show conflicting results[13]. Poor carbohydrate intake before and for the duration of the space flight may have negative effects on the crew’s performance and slow their response in emergency situations. If crew members have a deficiency in carbohydrates, their bodies will react and result in a ketotic state. It is very important to ensure that crew members are digesting sufficient amounts of carbohydrates or issues like ketosis can lead to more problems (for example, the life-support systems may struggle to remove exhaled ketones from the flight air)[13].
Bed rest investigations and observations show that flight and ground-based missions indicate changes in insulin secretion, insulin resistance, and glucose tolerance[13]. Even though these changes are subtle, scientists are studying the metabolic processes to evaluate the consequences of modified carbohydrate and insulin metabolism in space.
Proteins: Having a healthy supply of proteins is vital for every astronaut. In space, astronauts lose bone density (the longer the mission, the more loss) which is said to be associated with low-protein diets. A high protein diet can also cause harm so it is important that astronauts maintain a balanced intake. Some studies show that on long missions, it is common to see a pattern indicating that nominal protein intake levels have been reached or exceeded. However, short missions are said to show lower than recommended protein intakes due to insufficient food intake. Concerns are rising over the recovery period after short durations flights, as studies indicate protein as a limiting nutrient. Although it has not been tested experimentally, it is evident that good nutrition is a must for astronauts post-missions. On average, ISS missions show more than sufficient amounts of protein intake.
Fats: Scientific studies show that fish oils are essential to protect astronauts against muscle and bone loss and radiation risks. There exists a positive correlation between fish intake and bone loss, showing that those who eat more fish in space lose less bone mineral density[13]. Polyunsaturated fatty acids (PUFAs), such as omega-3 fatty acids, are typically included in the diet of an astronaut. Studies show that supplements of fish oils fail to display the same benefits as sources of food with such nutrients, highlighting the importance of dietary modification and not supplementation[13].
Canvas Quiz Question
Which of the following is NOT a common space food preservation method?
a) Thermostabilizing
b) Freeze dehydration
c) Intermediate-moisture food
d) Fermentation
d) Fermentation is the correct answer since all the other methods are commonly used to preserve space foods.
This question should be on the final exam because space travel is growing in popularity. We thought that this topic would be interesting to other students since some of these preservation methods were not covered in class, giving students more information about food preservation.
References
- ↑ “Food in Space.” Food in Space | National Air and Space Museum, airandspace.si.edu/exhibitions/apollo-to-the-moon/online/astronaut-life/food-in-space.cfm.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 “Preservation Methods Utilized for Space Food.pdf.” Preservation Methods Utilized for Space Food - MBA智库文档, doc.mbalib.com/view/5d4b2ed3053c6dff232650e6dc9d1b07.html.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Perchonok, M., Douglas, G., & Cooper, M. (2012, June 26). Risk of Performance Decrement and Crew Illness Due to an Inadequate Food System. National Aeronautics and Space Administration. https://humanresearchroadmap.nasa.gov/evidence/reports/Food.pdf
- ↑ 4.0 4.1 Oluwafemi, F.A., De La Torre, A., Afolayan, E.M. et al. Space Food and Nutrition in a Long Term Manned Mission. Adv. Astronaut. Sci. Technol. 1, 1–21 (2018). https://doi.org/10.1007/s42423-018-0016-2
- ↑ 5.0 5.1 5.2 5.3 5.4 Government of Canada. Canadian Space Agency. (2019). Eating in space.
- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 Perchonok, M., & Bourland, C. (2002). NASA food systems: Past, present, and future. Nutrition, 18(10), 913-920. https://doi.org/10.1016/S0899-9007(02)00910-3
- ↑ Zhitnitsky, D., Rose, J., & Lewinson, O. (2017). The highly synergistic, broad spectrum, antibacterial activity of organic acids and transition metals. Scientific Reports, 7(1). https://doi.org/10.1038/srep44554
- ↑ 8.0 8.1 8.2 8.3 8.4 Eating in space (2019, August 26). Canadian Space Agency. https://www.asc-csa.gc.ca/eng/astronauts/living-in-space/eating-in-space.asp
- ↑ 9.0 9.1 Doug, R. (2017. June 16). 5 Foods Astronauts Cannot Eat in Space. The Franklin Institute. https://www.fi.edu/blog/5-foods-astronauts-cant-eat-in-space
- ↑ Jitchotvisut, J. (2014, July 8). Taco Bell's Tortillas Are Extreme Enough For NASA. First We Feast. https://firstwefeast.com/eat/2014/07/nasa-launched-taco-bells-tortillas-into-space
- ↑ 11.0 11.1 Rodgers, M. (2019, July 11). 7 FOODS ASTRONAUTS AREN’T ALLOWED TO EAT IN SPACE. Everybody Craves. https://craves.everybodyshops.com/7-foods-astronauts-arent-allowed-to-eat-in-space/
- ↑ 12.0 12.1 12.2 12.3 12.4 12.5 Agency, C. S. (2019, August 26). Eating in space. Canadian Space Agency. https://www.asc-csa.gc.ca/eng/astronauts/living-in-space/eating-in-space.asp.
- ↑ 13.0 13.1 13.2 13.3 13.4 13.5 13.6 13.7 Smith , S. M., Zwart, S.R., Heer, M. (2014). Human Adaptation to Spaceflight: The Role of Nutrition . NASA. https://www.nasa.gov/sites/default/files/human-adaptation-to-spaceflight-the-role-of-nutrition.pdf.