Can storing fruits and vegetables in a dark cabinet or refrigerator lower their nutritional value? According to new research from Rice University and the University of California at Davis, there may be potential health benefits to storing fresh produce in areas that receive regular cycles of light and darkness.
The modular design of plants enables them to continue functioning as live plants even after they have been harvested. “Vegetables and fruits don’t die the moment they are harvested,” said Rice biologist and lead researcher, Janet Braam. “They respond to their environment for days, and we found we could use light to coax them to make more cancer-fighting antioxidants at certain times of day.”
Regular Cycles of Light and Darkness May Improve Quality of Stored Fruits and Veggies
A previous study by the same team found that Arabidopsis thaliana — a widely used organism for plant studies — begins increasing its production of insect-fighting chemicals a few hours before sunrise, the time that insects begin to feed. If this process continues after harvesting, the plant’s storage environment will have an effect on the health and nutritional value of the plant – both at the store and at home.
Braam’s team began their research by exposing harvested cabbage to regular light-dark cycles. The research team found they could encourage cabbage leaves to increase their production of anti-insect metabolites at certain times during the cycle. One of these, an antioxidant called glucoraphanin, is also a known anti-cancer compound that has been previously studied in broccoli and other vegetables.
Following the success with cabbage, researchers studied spinach, lettuce, zucchini, carrots, sweet potatoes and blueberries. Part of the experiment involved placing samples of lettuce and caterpillars in a chamber with controlled lighting. Researchers found that when the lettuce and the caterpillar were exposed to the same light-dark cycle, the leaves were less likely to be eaten. The lettuce produced anti-insect chemicals during the caterpillar’s normal eating time.
The findings suggest that storing fruits and vegetables in dark trucks, boxes and refrigerators may reduce their ability to resist insects and provide good nutrition. “We cannot yet say whether all-dark or all-light conditions shorten the shelf life of fruits and vegetables,” Braam said. “What we have shown is that keeping the internal clock ticking is advantageous with respect to insect resistance and could also yield health benefits.”
Braam’s team has already begun follow-up research, in cooperation with the Bill and Melinda Gates Foundation, to determine whether light and other external stimuli, such as touch, may be used to enhance pest resistance and the nutritional value of food crops in developing countries. “It’s exciting to think that we may be able to boost the health benefits of our produce simply by changing the way we store it,” co-researcher, Danielle Goodspeed, concluded.
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