The surprising findings should apply to other fresh vegetables and may offer insights into how to keep produce fresher longer, the researchers reported in the Journal of Agricultural and Food Chemistry.
They may also suggest ways to boost nutrients in fresh foods, says Gene Lester of the US Department of Agriculture’s Agricultural Research Service. He says the idea for the experiment came to him when he was shopping.
Supermarkets often display fresh spinach in clear plastic containers at around 4°C under fluorescent light 24 hours a day. Lester wondered if this was good or bad for the leaves.
“It is about time we asked some of these questions and do some of the science,” says Lester. …
His team kept fresh spinach leaves under continuous light or darkness for three to nine days.
Spinach kept under lights for as little as three days had significantly higher levels of vitamins C, K, E and folate, as well as more the colourful and healthful carotenoids lutein and zeaxanthin, they report.
Leaves stored in the dark lost nutrients, says Lester. On reflection, he says, the findings should not be surprising.
“These vitamins are basically in the plant for photosynthesis and we humans, being the biggest predator of plants, have evolved over time to utilise them as opposed to we having to manufacture them,” he says. …