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updated 11/23/2011 1:50:03 PM ET 2011-11-23T18:50:03

Aged beef? Sure, why not? Five-year-old peas? Not so much.

NASA has a long road ahead in its quest to be able to provide foods to astronauts with super-long shelf life, a necessity for missions to Mars and other destinations in the solar system.

Scientists recently tested 13 items that had been stored for three years, exposed them to temperatures of about 95 degrees Fahrenheit to simulate another two years of storage and then extrapolated the results to 65 entrees, based on the ingredients. Most of the foods are available to astronauts living on the International Space Station.

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"We don't have refrigerators and freezers for food and so all of our food has to be shelf-stable. We process it so it's either going to be thermostabilized like a canned product in a pouch, or it's going to be freeze-dried," said Vickie Kloeris, NASA's manager for the space station's food system.

The study showed that only seven items -- all meats -- would be edible after five years, said NASA food scientist Michele Perchonok, with the Johnson Space Center in Houston.

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“You can’t build a food system on seven items,” Perchonok said at the American Astronautical Society annual conference in Houston this month.

A five-year shelf life actually is a minimum, she added.

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A round-trip mission to Mars is estimated to take 18 months and the bulk of the food might be put in place before the crew even launches. Add on another year or two to produce and pack the food and that leaves scientists tasked to come up with processes and packages that will keep food viable for more than five years.

The longest-lasting foods in the NASA study were salmon and tuna, followed by pork chops, meatloaf and three chicken entrees. Vegetables fared the worst.

Thirty Johnson Space Center employees rated the foods on a variety of factors, including flavor, aroma and texture.

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“If it looked really bad, we decided we’re not even showing it,” Perchonok told Discovery News.

Sugar snap peas, rated acceptable from a health standpoint, didn’t pass muster.

"It was not nice. It was bitter and close to be unacceptable. I said 'We're not putting our people through this,'" Perchonok said.

NASA needs to develop foods with longer shelf life even if future space travelers harvest plants grown in habitats.

"If you're growing food and something goes wrong in that environmental chamber then what do you do?" Perchonok said.

The study is published in this month’s Journal of Food Science.

© 2012 Discovery Channel

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