According to a new review published in the Journal of Food Science, if National Aeronautics and Space Administration (NASA) is to send astronauts on extended missions, such as a proposed mission to Mars, then their food needs to be “nutrient-dense and long-lasting at ambient conditions”, while also being cookable under conditions of partial gravity.
Such challenges are being addressed by NASA Advanced Food Technology (AFT) scientists. Led by Dr Michele Perchonok, the scientists note that no US space vehicle, with the exception of Skylab, has ever been fitted with a refrigerator or freezer and therefore all foods must be thoroughly treated during processing to inactivate the micro-organisms responsible for spoilage. Unfortunately, such processing also has a detrimental effect on the nutritional and sensory aspects of the food.
“The change in mission duration for trips to asteroids, Mars, and other extended missions beyond low Earth orbit will necessitate an evolution of the food system. The Mars missions, in particular, will require development of technologies to enable the crew to be self-sufficient and less dependent on resupply missions,” wrote Dr Perchonok and her co-authors.
“One proposed mission to Mars designates use of the prepackaged foods, similar to those used on the ISS, for transit but may also include positioning food on Mars before the crew arrives. Under this scenario, prepositioned food may be 3 to 5 years old at the time of consumption.
“Achieving a 5 year shelf life to make this mission scenario feasible is an ambitious goal given that the current prepackaged foods have a stated shelf life of 18 months,” they added.
In collaboration with Maya Cooper from Lockheed Martin, and Grace Douglas from North Carolina State University, Dr Perchonok notes that the 2009 “Packaged Food Mass Reduction Trade Study” showed that it is possible to reduce the mass of a space food system mass while maintaining overall calories. This was achieved by “maximizing the percentage of energy from fat”, they said.
“With the additional fat, fewer grams of proteins and carbohydrates are necessary for an equivalent amount of energy and the total mass of food is reduced. In addition, sensory results showed that many of the thermostabilized foods could have the moisture levels decreased by 5 to 10 percent and maintain current taste acceptability,” they wrote.
The reduction in water content allowed the scientists to reduce the food system mass by 321 grams per crew member per day.
When this approach was subsequently extended to produce a meal replacement bar instead of a standard menu item, additional mass reductions were achieved. While both approaches are yet to be tested for their sensory acceptance, the study clearly shows the potential for longer term space flight, where feeding the crew is balanced with optimizing the mass of all on-board components.
“Increasing the fat content of foods often affects the shelf stability of the product over time,” cautioned Cooper, Douglas and Perchonok. “Artificial fortification of foods can lead to compromised nutrient delivery over extended storage time as well as create unpleasant tastes. These identified hurdles and those yet to be identified must be overcome to deliver the mass-reduced provisions required for viability of deep space missions.”
In terms of ensuring shelf life, one approach being considered by NASA food scientists is to use space as a natural freezer for foods.
“The cold temperatures would predictably halt any degradation of the food and provide a ready food supply to the crew,” explained Cooper, Douglas and Perchonok. “Because an actual mission destination has yet to be determined, there is little way to predict the radiation exposure and define the temperature ranges to which the food supply would be subjected.”
Work was slated to begin last year to study the effects of temperatures ranging from minus 80 to minus 40 Celsius on both food quality and the space food packaging.
Finally, ensuring vitamin delivery over five years of space travel poses significant challenges. Studies with various delivery forms, from tortillas to multivitamin tablets, the concentrations of certain vitamins have been shown to decline significantly during long-term storage.
“Encapsulated vitamin fortification or new methods of vitamin stabilization may be required to achieve nutrient-rich foods with limited degradation potential,” explained the authors. “Additional consideration will have to be given to the bioavailability of nutrients provided through the provisions to verify the adequacy of the nutrient concentrations in the proposed food system.”
Maintaining shelf-life, providing adequate nutrient intakes, ensuring safety after cooking and processing, as well as keeping masses and volumes to a minimum to safeguard mission viability continue to keep NASA food scientists busy.
“It is this delicate balance that frames the food system needs for our next mission and charts the work for NASA Advanced Food Technology,” they concluded.
Source: Journal of Food Science
Volume 76, Number 2, Pages R40-R48, doi: 10.1111/j.1750-3841.2010.01982.x
"Developing the NASA Food System for Long-Duration Missions"
Authors: Maya Cooper, Grace Douglas, and Michele Perchonok