The Navy looks at new technology for keeping produce fresh during lengthy voyages; see-through salad era may be over.
Justin Nassiri spent five years as an engineer in the Navy, living on submarines that would remain underwater for two or three months at a time. Although the Navy’s cooks would make sure to stock enough supplies for the trip, after about two or three weeks, the bowls of fresh fruit would be down to just a couple of green apples. And the lettuce in the salads would begin to look translucent from having been frozen and thawed.
Nassiri says on long watches, during which he’d stare out at the water through a periscope for hours at a time, he and his colleagues would sometimes play a game in which they fantasized about what they missed most. Nassiri says his list always included sushi, fruit and vegetables.
“I’d actually have daydreams of fresh vegetables — celery, radishes, anything,” Nassiri said. “It was really impressive what the cooks could do, but as ingenious as they were, you can’t fight nature. After three weeks, the salad would be see-through.”
Nassiri isn’t the only one daydreaming. Naval officials have been working with food scientists for the last two years to find ways to make fresh fruits and vegetables last longer. It’s not just about keeping sailors happy and healthy. It’s about waste. A few years ago, one naval official said his service was spending about $26 million a year on fresh fruits and vegetables, and then throwing out about $3 million because it had spoiled.
Fruits and vegetables respire like human beings. But when humans use energy, they replenish their reserves by eating. Fresh fruits and vegetables, on the other hand, have been separated from the plants on which they grew and can’t generate new energy reserves.
The trick to keeping fruits and vegetables alive longer, then, lies in slowing down the amount of energy they expend, and that is done by reducing their metabolism or respiration rate — the rate at which they take in oxygen and release carbon dioxide. That’s usually achieved in two ways: by keeping the produce at a low temperature — 32 to 55 degrees Fahrenheit, depending on the fruit — or by modifying the atmosphere in which fruits and vegetables are stored.
Navy officials are working with a food technology company in California, Apio Inc., which has a product, BreatheWay, that controls the ratio of oxygen to carbon dioxide moving in and out of a package. The ratio is regulated via a membrane placed over a hole or window in the packaging. The membrane helps maintain an appropriate ratio of oxygen and carbon dioxide inside the package, depending on the type of fruit or vegetable being stored. The oxygen level in the air of an ordinary room, for instance, might be 20.8 percent, while the oxygen inside a modified-atmosphere package might be as low as 3 percent. The level of carbon dioxide inside the package might be 4 to 6 percent, while it might be near zero percent outside.
BreatheWay also has a temperature switch that increases or decreases permeability in the packaging, depending on the temperature at which the package is stored. By slowing down how quickly the produce uses its energy reserves, scientists can make it live longer. Keeping fruits and vegetables healthy also inhibits the growth of organisms that decay produce.
“When you harvest a fresh vegetable or fruit, it has a reaction to being separated from the sustaining tree or plant, and that wound makes it respire faster. It’s panicking, if you will,” says Cali Tanguay, business development manager at Apio. “You’re trying to create an environment that’s as moderate as possible.”
In trying to determine which technology to use, the Navy conducted food-freshness tests on two aircraft carriers — the USS Ronald Reagan on the West Coast and the USS George H.W. Bush on the East Coast — in February and October of 2008, using broccoli crowns, cantaloupe, honeydew, iceberg and romaine lettuce, bananas and tomatoes. The Navy chose products that were in high demand by sailors, that seemed to respond well to the technologies being tested and that were not easy to replace with canned or frozen versions.
The results were a smashing success, naval officials said. The cases lined with Apio’s product enabled the Navy to extend the shelf life of fresh fruits and vegetables greatly, according to Gerald Darsch, director of the Department of Defense’s Combat Feeding Directorate. Lettuce, for instance, lasted 70 percent longer, cantaloupe 150 percent longer, and broccoli a whopping 300 percent, Darsch said.
“I traveled with one of my co-workers, and she got a big hug from the supply officer on the USS Reagan,” Darsch said. “They noticed they had bananas to eat well into the deployment. In the past, they barely got away from the pier before the bananas were gone.”
The Navy conducted another test in November on fruits and vegetables sent in commercial shipments to military bases in Guam. It created three scenarios: The first container was simply refrigerated, with nothing done to the atmosphere inside. The second container was refrigerated and filled with a specific mixture of oxygen and carbon dioxide. The third container was refrigerated, and the individual cases of produce were lined with Apio’s product. At the end of 38 days, only 58 percent of the broccoli in the first container was usable. In the second container, 79 percent of the broccoli was good. And in third container, which used Apio’s technology, 94 percent of the broccoli was edible.
But if early tests have been successful, logistics still have to be addressed. The military can be highly secretive about the locations of its ships and submarines. Naval officials wouldn’t even disclose the locations of the aircraft carriers on which the produce technology was tested. Sometimes, officials don’t know where a ship will be in a week.
It was just these kinds of logistical issues that made it difficult to test the technology on submarines, even though they’re likely to be one of the biggest users of the products. The problem that makes it difficult for them to stock up on fresh produce — they move out of reach of ports and supply ships for extended periods of time — also made it difficult to get nonmilitary personnel on board for product testing, which is why the trials were conducted on aircraft carriers. There are also problems with space — particularly on submarines — and loading processes, which can result in produce being left to sit out on a hot dock for hours, losing valuable shelf life.
“The bottom line is, this all adds a step of complexity,” Apio’s Tanguay said.
The military has also been looking at technologies to remove ethylene gas from fruit and vegetable packaging. Produce gives off this gas naturally as it ripens, and ethylene signals fruits and vegetables to ripen; too much makes produce ripen too quickly and rot.
The Army has been testing a product developed by a Massachusetts-based company, Primaira LLC, which uses an electrical device to convert ethylene gas into water and carbon dioxide. The product was put into a shipping container with broccoli and apples, and after seven days, the broccoli had lost only 20 percent of its firmness, compared to a 60 percent loss without Primaira’s technology, says Karen Benedek, managing partner at Primaira. Naval officials plan to test the Primaira device this year and hope to use it on aircraft carriers, where, if the new freshness technologies work, see-through salad will be deep-sixed, rather than eaten.
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