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Summer Produce Could Last Longer With These Five New Technologies

Scientists seek solutions to slow the inevitable process of decomposition

Haiqiang Chen tests his UV oven at the University of Delaware (Wenbo Fan)
smithsonian.com

Every summer, fresh produce floods farmers markets and fruit stands—peaches, tomatoes, zucchinis galore. And the race is on for consumers to pack away all the fresh vegetables and fruit before the inevitable takes over: decomposition.

But the problem isn't limited to the hot summer months. Grocery stores in the U.S. toss out 43 billion pounds of food each year, much of it because it’s past its expiration date or peak freshness. That’s one reason food scientists have been working to improve the shelf life of fresh food, and in the past month they’ve made some big breakthroughs. Here are a few recent projects that could help you hang on to your Mortgage Lifters and Green Zebras a little bit longer in the future.

Tomatoes

Tomato aficionados know timing is everything. Slice into one of the red (or yellow, green, purple or orange) beauties before they’re ripe and you miss the sweetness; wait too long and it will rot away seemingly overnight. But a new study published in the journal Nature Biotechnology suggests that an era of long-lasting, delicious tomatoes may be near. According to Ria Misra at Gizmodo, researchers at the University of Nottingham identified the specific enzyme, pectate lyase, that causes tomatoes to self-destruct and turn mushy. Researchers found if they turn off the gene that produces the enzyme, the tomatoes stick around much longer. Study author Graham Seymour tells Misra modifying the tomatoes this way has no effect on their flavor or sugar content.

Milk

Once milk is pasteurized, a process in which it is heated to at least 145 degree Fahrenheit for 30 minutes, it has a shelf life of about 3 weeks before it goes off. But a study published earlier this month in SpringerPlus shows that a simple modification to the process can significantly boost its longevity. Bumping the temperature by 10 degrees Celsius for less than a second kills off even more bacteria than pasteurization, including the bugs that eventually cause milk to spoil. “It’s an add-on to pasteurization, but it can add shelf life of up to five, six or seven weeks to cold milk,” Bruce Applegate, the Purdue researcher who developed the process says in a press release. “With the treatment, you’re taking out almost everything. Whatever does survive is at such a low level that it takes much longer for it to multiply to a point at which it damages the quality of the milk.”

Apples

“Fruits or vegetables turn bad mainly due to the bacteria,” Xinpei Lu of China’s Huazhong University of Science and Technology tells Misra. “That’s the reason why we keep fruits [at] either a low temperature, or in nitrogen gas, or vacuum packed to avoid the growing of bacteria, and thus to extend the shelf-life.”

If bacteria does find the fruit, it often forms a biofilm, quickly leading to rot. Previous research showed that cell membranes rupture when exposed to plasma, the ionized gas used in plasma TVs, neon lights and other applications. So Lu and his colleagues exposed apples to plasma and found that it kills the biofilm bacteria without harming the fruit. The researchers estimate the process could keep fruit fresh for several more weeks. The next step is to develop a cheaper way of making plasma and developing a plasma scanner that could treat a range of both fruits and vegetables.

Mangos

The problem with many fruits, mangos included, is that they all ripen at once—many of them are rotten before hitting the plate. But Jay Subramanian at Guelph University, Ontario is working on a nanotechnology spray that could change that. According to Bryson Masse at Motherboard, fruit ripens when an enzyme starts breaking down the cell membrane. That allows in the hormone ethylene, which starts the ripening process. But a naturally-occurring compound, hexanal, keeps the cell membranes tight, preventing ripening from commencing. Subramanian tested a hexanal spray on mango trees in India. The chemical delayed ripening by two to three weeks with no negative effects on the fruit. Delaying the fruit allows farmers to stagger their shipments of produce, which lets them avoid glutting the market. Farmers in the test earned 15 percent more from their mangos, which had a shelf life of about 26 days in cold storage. Other tests of the spray on tomatoes, broccoli and flowers were also successful.

All Produce

These days, produce recalls related to salmonella, E. coli and listeria seem to make headlines every few days. That’s one reason Haiqiang Chen at The University of Delaware developed his new UV oven. Chen is perfecting a device that looks like a microwave, but zaps food with UV light, a process that kills germs without producing heat. “There’s been nothing that’s really effective that you can use at home to ensure clean produce,” Chen says. So this new product fills that gap.

The UV box is also perfect for cafeterias, restaurants and commercial kitchens to ensure food safety. In tests, Chen’s device killed 99.7 percent of salmonella bacteria on lettuce, spinach, tomatoes, blueberries and strawberries. Washing with tap water only reduced the salmonella by 59.3 percent.

About Jason Daley

Jason Daley is a Madison, Wisconsin-based writer specializing in natural history, science, travel, and the environment. His work has appeared in Discover, Popular Science, Outside, Men’s Journal, and other magazines.

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