Electrified Lettuce Stays Fresh, Tests Show

When smart shoppers select a head of lettuce, they automatically set aside the ones that have blackened edges to their leaves and think no more about their fate. But greengrocers and the big supermarkets chains do, because at the end of the day they have to toss out all the rejects, which can mean big losses. But now, a discovery by a Hebrew University scientist may mean an end to the black days of lettuce.

Prof. Amos Nussinovitch, of Hebrew University's Faculty of Agriculture in Rehovot, discovered during his research on dehydrating vegetables that a gel made of a vegetable-based polymer lost liquid and shrunk when electrified. He assumed that real vegetables would also react this way. He was right.

"We began by electrifying potatoes that had been placed in water," explained Nussinovitch. As a result, much of the liquid that made up the potatoes seeped out." Nussinovitch realized that he had come across a new method of dehydrating vegetables in liquid. Then, he noticed an added value to the method: the electrified potatoes did not darken as quickly as normal, keeping their fresh-peeled color for up to 24 hours.

Potatoes, of course, are not sold peeled, and so their shelf life is longer than the leafy green salad staple, which starts to darken even before discerning shoppers make their choice.

So Nussinovitch and doctoral student Ronit Tzvitov built an apparatus in which they soaked the base of the lettuce in water and inserted two electrodes into it that are connected to an ordinary AA battery. Then they turned on the current for less than a minute. The lettuce reacted just like the potatoes, with no black edges in sight.

Nussinovitch and his team have been working on the project for two years. Yisum, the Hebrew University subsidiary that seeks commercial applications for the intellectual property of its scientists, is now looking for companies interested in turning the lettuce electrification process into a commercial product.

"At this point it's hard to say if there is tremendous interest in the market," said Nussinovitch, "but I hope there will be. After all, this is a short, simple process. A small farm only needs a few pieces of this equipment, and farmers can insert the lettuce by hand. Larger farms will probably want an automatic system," he said.