Maintaining Biological Clock in Fruits, Veggies Increases Nutrients Post-Harvest

Biological clocks in vegetables and fruits continue to tick even after harvest. A team of researchers found that storing fruits and vegetables in a continuous day-night cycle of 24 hours can boost their nutrients.

The study was conducted by experts from the Rice University and the University of California at Davis who showed that internal clocks in vegetables and fruits can be controlled with different light settings. Since, the internal clock decides what chemical a vegetable or a fruit is releasing; storing them in a light-dark cycle can release disease fighting chemicals in the produce, like those that fight cancer.

In one of the experiments, researchers controlled light exposure to the plants and manipulated them into releasing insect-fighting chemicals. One such chemical called glucoraphanin, or 4-MSO, is a cancer-fighting agent.

"Vegetables and fruits don't die the moment they are harvested. 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," said Janet Braam, biologist from Rice University and the lead author of the study.

This research is a follow-up of the team's previous study on circadian rhythm in plants. Scientists had then found that plants use biological clocks to defend themselves against insects. This study was conducted on Arabidopsis thaliana, a plant related to cabbage.

The present study was conducted on cabbages which found that the internal clock could be reset even after harvest. They then performed similar experiments on spinach, lettuce, zucchini, carrots, sweet potatoes and blueberries and found that plants can be put on their normal circadian rhythm by keeping them in a closed chamber with controlled lighting.

Experts aren't sure if keeping fruits and vegetables in dark or refrigerating them shortens their shelf-life, but say that maintaining the plants' biological clock could extend their life post-harvest and increase nutrition value.

"We cannot yet say whether all-dark or all-light conditions shorten the shelf life of fruits and vegetables," Braam said in a news release. "What we have shown is that keeping the internal clock ticking is advantageous with respect to insect resistance and could also yield health benefits."

The study is published in the journal Current Biology.