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Question: How to preserve food (preferably in ready to eat form [MRE]) for 200-300 years on a spaceship?

Bonus objection: preserve viable seeds for the same period

Requirements

MREs should contain all necessary nutrients to sustain humans for a period up to a year without significant and irreversible health problems. All humans are healthy adults working in 8h-long shifts per 24h cycles. Most of the work is not physically demanding, but humans should keep good physical fitness in case of emergency EVAs.

Cooking is not impossible but not desirable, as MREs are meant for emergency and early wake-up crews.

For the duration of the voyage, only micro-gravity in a few small modules is possible and most of the ship interior does not have an atmosphere, but they can be pressurised on demand. Once the colonists reach their destination the entire ship has to have an atmosphere to allow for arrival operation procedures.

Available technologies

  • suspended animation based on induced torpor [aka hibernation] (this method cannot be used to preserve plants or dead tissues, it works only for living organisms with the sufficiently developed nervous system);
  • advanced robotics and automation (the spaceship can travel on auto-pilot for decades, all routine maintenance tasks can be performed by automatic systems, including various bots and drones, but emergencies still require human intervention);
  • genetic engineering (mostly CRISPR and similar technologies);
  • artificial meat (can be grown in labs, once they are in operation, but the ingredients should be produced or stored beforehand);
  • all currently available technologies and those that are currently in development, but not finished, yet.

Things that cannot be done:

  • there is no cryosleep or any other super-technology that allows freezing and unfreezing without any damage (unless some similar technology already exists or is in development and I just do not know about it);
  • there are no food synthesisers or 3D printers that can print food or complex molecular structures (all plants and animals are sequenced, but it is not possible to recreate them from DNA blueprints, they have to be physically present in some form);
  • there is no AI that could take care of artificial biosphere and keep it going for 2-3 centuries (a permanent algae farm or similar is, however, probable).

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Feel free to ask for additional details or clarification if necessary.

P.S. This is not a duplicate question. While there are other questions regarding food preservation in space, they have fewer constraints and proposed solutions cannot be applied to this particular case.

P.P.S. Food is one of the most important elements of my project, so handwaving is not really an option.

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  • $\begingroup$ Why can't you just say "MRE's" and state that they have a really long shelf life. If you need to, explain that the MRE's are frozen until shortly before being used. $\endgroup$ – NomadMaker Aug 22 at 7:20
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    $\begingroup$ If they have the technology to preserve a living human for that long they can can preserve food for that long. A living humans has all the problems with storing food plus a thousand more, it is literally impossible for them to be able to store humans and not food. $\endgroup$ – John Aug 22 at 22:17
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    $\begingroup$ @Otkin torpor also doesn't allow for digestion or any kind of material replacement, you can't have torpor for hundreds of years unless you can feed the bodies during it AND you have a way to prevent the effects of aging. the scientific needs for long term torpor is even greater than just frozen cryosleep. It also means you need a functioning ecosystem just to keep supplying them with oxygen. If you can engineer torpor in humans you can make plants that don't need super intelligent AI to tend them. $\endgroup$ – John Aug 23 at 3:19
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    $\begingroup$ @elemtilas This is a sleeper ship. The entire crew is in induced torpor (no fancy genetic engineering, technological methods). There are an emergency and an early wake-up crew who need MREs. Emergencies are few and rare, but the early wake-up crew will be working on setting up habitats and food production. Estimated time of completion for these arrival procedures is 1 year. But the MREs need to supply all necessary nutrients only for the first 6 months. The first leafy greens can be grown by that time. Of course, some redundancy is required, so the total food supply carried by ship [cont.] $\endgroup$ – Otkin Aug 23 at 18:35
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    $\begingroup$ @elemtilas […] should be around 2 years worth of balanced nutrition for the entire crew. The crew is not made of men and women of steel. They are trained for space but they are not professional astronauts. Most of them are scientists. Considering psychological problems associated with space, isolation, and habitation in close quarters, it is my desire to provide them with meals that are nutritious and are as close to regular food as possible. If it is possible to accomplish, of course. There are no resupply ships or mission control. They are completely on their own once they leave Earth orbit. $\endgroup$ – Otkin Aug 23 at 18:44
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The regular methods.

Food spoils by microbial action. Food spoils by intrinsic fast chemical reactions like oxidation of fats. Food spoils by slow chemical reactions, like degradation of vitamins to inactive molecules.

  1. Food is irradiated. No microbial life remains.

  2. Food is dehydrated. Most chemical reactions occur in the aqueous phase and without water, they will not occur.

  3. Food is sealed from oxygen. With no water and no oxygen, oxidation must occur only via any oxygen molecules already in the food.

  4. Food is frozen. Wrapped, prepared food will be stored in reflective packages containing radiators, within the spaceship but outside conditioned habitable quarters. It will be under vacuum. It will be cold. The colder it is the slower any chemistry happens.

  5. Food is generally not cooked. Cooking can break down vitamins. These foods will be raw.

Even under terrestrial circumstances, desiccated frozen mammoth meat is edible after thousands of years. So too your foods. For example: a reasonably well prepared & sealed container of food (pemmican, chocolate, salt & pepper) can be perfectly edible after more than a century. And even a bit of hard tack approaching two centuries!


Side note re vitamins. I can understand concerns that these would not last a century. One can engineer yeast to synthesize all the vitamins we need. I can imagine a bottle of ice with nutrients and freeze-dried yeast in the cap. On cracking it, one shakes it up and lets it sit for a day. The yeast come to life and do their thing and viola! - instant yeasty vitamin water!

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  • $\begingroup$ Blanching (heat treatment) is necessary for almost all fruits and vegetables that can be frozen relatively easy. Blanching destroys enzymes that play an important role in food degradation. Low temperatures reduce enzyme activity but do not stop it completely. Irradiation and dehydration cause loss of nutrients (ucanr.edu/datastoreFiles/608-216.pdf). $\endgroup$ – Otkin Aug 23 at 1:57
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    $\begingroup$ @Otkin they cause a reduction not a complete loss which means you can brute force through the problem, just use fortified foods. $\endgroup$ – John Aug 23 at 3:21
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    $\begingroup$ @elemtilas Thank you for the example. There are several other things that can be kept almost indefinitely or sufficiently long for my purposes. Raw honey, salt, sugar, soy sauce, white rice, and some low oil grains can be stored for centuries. They would provide dietary fibre and carbohydrates, but it is not enough for a healthy diet, especially for people who need to perform well. My main concerns nutrition-wise are oils and micro-nutrients. These do not store well and tend to spoil or degrade. $\endgroup$ – Otkin Aug 23 at 18:52
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    $\begingroup$ I am starting to lean toward permanent algae farms run by AI. They might be my best bet to provide nutrition supplements in an accessible and easily digestible form on demand. Yeast is also a neat idea, thank you. $\endgroup$ – Otkin Aug 23 at 19:14
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    $\begingroup$ The point about mammoth meat being edible is an interesting one, but I wonder how much nutritional value it still has (due to some combo of complex molecules naturally breaking down with time, and some being consumed by extremophile bacteria that survive those temps). This article claims that meat which is both vacuum-sealed and kept in a freezer can last about 3 years, though not sure if after that it's just a problem with freezer burn or if it "goes bad" in a worse way. $\endgroup$ – Hypnosifl Aug 27 at 22:31
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Starship grade freezers store at near absolute zero so just do that. Even a few Kelvin would probably do. I don't know why you're concerned about freezing and unfreezing without "damage". This is food, not a living thing. It's just freezer burn.

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    $\begingroup$ Thawing process causes molecular changes to tissues and affects cell structure. It leads to changes in taste and texture of food. Which is unpleasant but can be tolerated for some time. My biggest concern, however, is the loss of nutrients. For example, vitamin C is lost not only during pre-freezing processing but also during storage as demonstrated in this article (ucanr.edu/datastoreFiles/608-742.pdf). The latter is negligible if we are storing for 6 months, but in 200-300 years the accumulated loss can be very significant. $\endgroup$ – Otkin Aug 22 at 19:29
  • $\begingroup$ @Otkin Which is why you don't freeze it as normal freezing temperatures. $\endgroup$ – DKNguyen Aug 22 at 20:57
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    $\begingroup$ Do you have any sources that support an idea that nutrient loss is non-existent under temperatures close to absolute zero? $\endgroup$ – Otkin Aug 23 at 1:59
  • $\begingroup$ Inherent to the definition of absolute zero is the lack of chemical reactions, though there are apparently weird non-chemical changes that can occur but these are a lot slower than the actual chemical reactions normally associated with degradation. $\endgroup$ – DKNguyen Aug 23 at 4:17
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    $\begingroup$ @Otkin I've worked in research, and we freeze all sorts stuff in liquid nitrogen almost indefinitely. as long as the containers are completely sealed. No one has done centuries-long studies on this so it's kind of hard to absolutely prove. At near absolute zero, atoms are barely moving and should reasonably last centuries. Your vitamins can be purified, dessicated, made into pills and THEN frozen if you have degradation issues. $\endgroup$ – DWKraus Aug 23 at 4:28
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Main Problems

Hibernation is not Stasis

Hibernation or induced comas as we call it in humans alone will not keep people alive for 200-300 years. In these states, animals continue to age and consume resources. This could be used to reduce the amount of food your population needs on the trip, but they will still starve to death and/or die of old age meaning you do not have the technology to keep these people alive in this state as described.

So, you will need to do some hand waving to explain how a person can survive a 200 year coma without food or aging.

Lose of Essential Nutrients

There are many foods with very long shelf lifes that are considered "non-perishable" but this is a relative term. While some food remains edible for centuries, no food retains certain very important nutritional qualities past 15-30 years. The most notable being omega-3 fatty acids, vitamin-c, and the 9 amino acids that our bodies cannot synthesize on their own. These will break down within this timeframe regardless of what well researched food preservation method you use¹. Failure to preserve these elements would result in health problems including neurological and muscular degeneration and scurvy.

As for seeds, you will need to freeze them to very low temperatures to maintain viability after 300 years. Cryogenic freezing lacks the research to accurately prove the viability of seeds past 20-30 years, but the predictive evidence suggests that freezing to temperatures of at least -135°C may result in you still having a significant number of remaining viable seed after 300 years².

Possible Solutions

Time dilation

Time dilation can solve both your food and hibernation problems, but getting enough of it may be outside of your intended tech level. If your ship travels very close to the speed of light, you can slow down the experience of time for the crew. At 0.999999C, the crew would experience a 300 year trip as only being about 5 months long. This is probably outside of the tech level you are looking for, but in this case humans could remain in medically induced "hibernation" (hibernating mammals can typically survive 5-6 months without eating) and their food would still contain plenty of essential nutrients to sustain good health by the time they reach their destination.

Advanced Artificial Organic Compound Synthesis

If your ship has the technology to create its own organic compounds, then this could also help with both problems. Your hibernating crew needs to do more than just sleep. They need 100% of their biological substance slowly recycled back into their body. Through the application 100% recycling, the ship could in theory uptake all of a sleeping person's feces, sloughed off skin and hair, and urine, and turn it back into essential proteins, lipids, carbohydrates, and other micronutrients to keep a person alive off nothing but their own atoms + a bit of electricity. A civilization with this level of bio-chemistry knowledge would probably also have the technology to manipulate the daf-2 gene to halting the aging process.

Things like rice, dried beans, and processed sugars have all been proven to be edible after hundreds of years. Honey too. So, you can just bring these and re-add essential nutrients when you reach your destination using the same general technology.

This might not work with your plot though, because this tech would essentially eliminate the urgency of having a stored food supply; so, you'd have to somehow address why they can't just stay plugged in while their first crop grows.

Adopt a Hybrid Generation Ship Model

I think this would work best with your plot and described tech level.

Because they have hibernation based statis, your crew can spend a lot of time asleep conserving energy. This means your ship may not have enough aeroponics farms to feed everyone at once, but it will have enough to feed some of your crew at any given time. Let's say for the sake of argument, that your crew needs to sleep for 5 months at a time, and then wake up for 1 month to eat, exercise, and do all the things they need to do to get their bodies fit for the next hibernation cycle. In this case, a ship with food production capabilities for 100 might be able to transport several hundred colonists .

On the final growing season of your journey, your crew can focus on a crop that is extra high in essential Amino Acids, Omega-3, and Vitamin-C. That way, when everyone wakes up at the same time, this crop can be used to supplement the nutrient deprived stored foods while also placing a sense of urgency on getting their first crop going since their ship is not designed to grow enough for everyone to survive off of.

You'd still need to address the issue of aging, but again, if you manipulate everyone's daf-2 gene before they leave Earth, it's possible these humans have just been genetically altered to be able to live for hundreds of years. Because scientists have already identified the gene associated with aging and a few mutations that are known to slow it down significantly, this may not be as future tech as it sounds.


1. By this I am referring to well researched and commercially approved methods of storing food. Dehydration of food to 5-16% water content, freezing of food to anywhere as cold as -40°C, canning, chemical preservation, etc. Cryo-freezing to temperatures below -80°C can preserve amino acids seemingly indefinitely, but the only methods I can find that involve freezing to that low of temperatures that preserver lipids like Omega-3 require adding chemicals that are toxic to humans; so, you could not eat the food when you are done. Research footnotes that I've found suggest that Vitamin-C is also vulnerable to cryo-freezing; though, I can't find anything that explains how much so. New cryogenic freezing methods are being researched all the time; so, slight improvements to modern tech might preserve your food's nutrients for 300 years, but this would would require the OP to relax his/her no advanced cryotech stipulation.

2. According to this research paper, you would probably have about 10-80% of your seeds left germinating at -135°C and 25% or more of your seeds at -196°C. That said, it is important to note though that when extrapolating data this far past your data set you can not predict any criteria that would cause a spontaneous future failure of your whole seed stock.

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    $\begingroup$ I'm gonna mark this whole answer with [CITATION NEEDED]. Define "significant nutritional value". It might not be super healthy but enough basic nutrients, like sugar and fat, must remain if something "remains edible" that I'm skeptical everyone will be in danger of dying from malnutrition inside of 15 years. Essential vitamins, minerals, and other micronutrients should be easy enough to synthesize. I'm not sure rock candy if kept dry has a meaningfully-restricted shelf life at all, never mind 30 years. Over 2-3 hundred years, it might start to chemically decay. $\endgroup$ – Ton Day Aug 26 at 7:37
  • $\begingroup$ I second @TonDay with [Citation needed]. I also want to point out that we are not talking about a generation ship. If it were the case there would be no need for food preservation at all. $\endgroup$ – Otkin Aug 26 at 8:13
  • $\begingroup$ @Otkin re-read the OP, "200-300 years on a spaceship?" and "there is no cryosleep" it's pretty clearly a generationship, just not one that grows its own food. $\endgroup$ – Nosajimiki Aug 26 at 15:43
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    $\begingroup$ Um, honey is definitely food and has nutritional value. You can survive for maybe a month or two on just honey and water without permanent damage and honey can store for thousands of years. The oldest honey samples we have are >5000 years old and it's not spoiled or anything. Stored properly, it would probably literally last forever $\endgroup$ – Dragongeek Aug 26 at 16:48
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    $\begingroup$ @Nosajimiki I am the OP. $\endgroup$ – Otkin Aug 26 at 17:19
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This is not an answer, but rather my thoughts on the subject that I decided to share after getting initial responses to my question.

There are three main considerations when it comes to food preservation:

  • nutritional value (macro- and micronutrients);
  • texture and taste;
  • presentation (colour, serving sizes, decoration, etc.)

Available food preservation techniques negatively affect all three aspects. Nutrients are destroyed during preparation for storage and during storage itself, texture and taste may be altered, and presentation may suffer greatly as well. I was looking for ways to negate (to some degree) all three as food is critical for the physical and psychological well-being of humans, especially in space.

Macro- and micronutrients

Preservation of nutrients is the most important aspect since there is no external source that could provide missing ingredients. As we know from history and modern research, nutrient deficiencies lead to deterioration of physical and mental health and ultimately death.

While there are some types of food that can be stored sufficiently long for my purposes, they would not constitute a balanced diet. A non-exhaustive list includes raw unfiltered honey, soy sauce, refined sugar, salt, white rice (some varieties), cornstarch, vinegar, pure vanilla extract, low-oil grains, dried tea leaves, cacao, and powdered milk (if frozen).

My research of modern food-preservation techniques (canning, freezing, irradiation, dehydration, controlled atmosphere, chemical additives, fermentation, extraction, and so on) suggests that none of those methods is effective for long-term storage measured in centuries. While it is possible to preserve macro-nutrients, especially, carbohydrates, the degradation of micronutrients, most notably, vitamins poses a big challenge.

Willk's proposed answer is based on the use of these techniques and their combination. It is a good common-sense approach, but it ignores evidence that, for example, blanching is necessary before freezing for many plant-based foods. Blanching is a heat treatment (may reduce Vitamin C content up to 90%) that deactivates enzymes responsible for certain types of food degradation. Enzyme activity does not stop even if food is frozen, it only slows down. Moreover, enzymes become more active during defrosting. (Humans cannot consume all food frozen, so defrosting is necessary and should be included in any discussion of food preservation for later consumption.) Likewise, irradiation and dehydration also lead to the loss of nutrients.

As discussed with DKNguyen, freezing also does not stop the deterioration of nutritional value. Vitamin C, for example, continues to degrade at freezing temperatures (-20C). The loss of nutritional value in cold storage as shown in the linked source is negligible when we store for 6 months. However, losses accumulated over a period of 2-3 centuries may be very significant. It is likely that rapid freezing and storage at near absolute zero can arrest some of this deterioration, but so far there is no scientific proof for this.

Freezing also causes denaturation of proteins, which affects some groups more than the others. This may have negative effects on nutritional value and digestion. More research on my part is needed to clarify this in greater detail.

Some commenters suggested using dietary supplements to make up for losses in the nutritional value of stored food. This seems like a reasonable suggestion, but it may pose problems due to bioavailability and drug interactions of the said supplements. Micro-nutrients in food and pills are not always chemically the same and are not processed by human bodies in the same way. Dosages should be calculated very precisely and depend on a big number of factors such as genes, microbiome, diet, and even mood. It is also observed that multi-vitamin supplements can increase the risks of cancer and cardiovascular diseases.

I am going to do more research, but it seems impossible to preserve the nutritional value of food at high enough levels with contemporary or slightly more advanced technology. Some supplementation is necessary. It also looks like crew members would require close observation and individualised solutions until food production is fully established to prevent nutritional deficits.

Texture and taste

Texture and taste are extremely important. If people do not like them they are not going to eat their food or not going to eat enough of it.

Food texture is often downplayed or completely ignored, but it affects taste a lot and for many people is a decisive factor in food preferences. I, for one, cannot eat anything resembling porridge: a sticky substance with pieces of something more solid in it. Even thinking about it makes my stomach sick. Moreover, the awareness of food texture is often subconscious, so it may have a profound impact on the perception of food and psychological adaptation and well-being of space travellers.

As for the taste of food, astronauts report that it changes in micro-gravity. This, most likely, can be attributed to physical changes that happen to human bodies in such conditions and loss of sense of smell. Some astronauts complained that sweet food, especially with added sugars, was too much for them. It is also known that spices and spicy sauces are very popular on ISS as they help to overcome the blandness of the food.

Food preservation techniques often lead to changes in texture and taste. Some of them are intentional and some are not. Unintentional changes are usually related to the cellular and molecular damage resulting from preparation for storage, storage, and preparation for consumption (defrosting, hydration, etc.).

Ice crystals formed during freezing (even rapid freezing produces ice crystals, albeit smaller) damage cell walls. This reduces firmness of the fruits and vegetables and leads to loss of nutrients and altered taste due to drip loss. The scale of damage depends on freezing methods, species, and specific cultivars.

Freezing also causes denaturation of proteins, which is especially damaging for animal-derived food. For example, frozen fish may lose taste, change colour, and become tougher. This process also reduces the bioavailability of proteins, thus diminishing nutritional value.

Damage to the packaging of frozen food may lead to the loss of moisture and 'freezer burn'. While it does not make food unsafe per se, it makes food tougher and creates eating experience akin to chewing leather or wood. This is highly undesirable in an already stressful environment.

Presentation

Presentation of food is another important aspect of preservation. Food that tastes great and has high nutritional value still will not be consumed enthusiastically if it does not look good. Shared meals are also important for morale and teamwork.

This is something that I still need to research. Of course, there are limitations on serving methods available in micro-gravity and a restaurant-style meal would not be possible even if I could teleport it to the ship. I still believe that it is possible to come up with something that will be more exciting and pleasing to eat than nutripaste or soylent green.

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At this point, I am leaning toward freeze-dried food rations kept at near absolute zero supplemented by permanent algae and yeast farms. Algae and yeast cultures are relatively easy to maintain, so this can be done by automatics and supervised by the emergency crew members in extraordinary circumstances. Algae and yeast also have a benefit of easier storage and farms can be scaled up as demand increases. There should also be fewer problems associated with micro-gravity. An additional benefit is that algae farm is a proven technology not just for food, but for other life-support systems, and it was already included in my world design.

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    $\begingroup$ note damaged cell walls do not reduce the nutrition of frozen food, just the taste/texture. $\endgroup$ – John Aug 28 at 1:10
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Why not fill your micro-gravity modules with genetically engineered food forests using artificial light, robot gardeners and simple machines to turn O2 into CO2 so that the plants thrive. This way your crew will wake up to not only food but also oxygen.

Include enough varieties of seasonal crops and vary the lighting schedule in each module so that some food is always ready for harvest. Then while your crew sleeps, process the fruit to create fertilizer and seeds so the robots have materials available to keep the garden going.

Fruits and Vegetables are the original "Meals Ready To Eat".

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  • $\begingroup$ Algae is a much more efficient approach to CO2, water, and O2: smaller footprint, lower light requirements for the same output, and easier to control. Farming, on the other hand, is not that easy. There are many variables to consider and each variety of crops requires it is own conditions for optimal growth. Aeroponics is one of the most suitable approaches to growing food in space, but it may cause problems down the road. Without humans to feed aeroponic farms would just drain resources. It is close to impossible to create a stable biosphere in a small closed environment. $\endgroup$ – Otkin Aug 28 at 0:20
  • $\begingroup$ @Otkin but it is a LOT easier than keeping a human body alive for the same amount of time, so it is completely reasonable they could do it. $\endgroup$ – John Aug 28 at 1:00

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