Spinach leaves that have been frozen will inevitably wilt, turning into an unappetizing mush.
Researchers in Sweden have developed a new method of freezing fresh vegetables and fruit keeping cells alive which they say preserves their firmness and taste after defrosting.
Trehalose, a natural sugar found in yeast, fungi and grass types that survive cold winters better than plants and vegetables, and prevents cells from breaking down when ice crystals form.
The idea is to put the vegetables inside a vacuum machine to extract the air within them.
The air is then replaced with water containing the trehalose and a small electrical pulse is applied to the vegetable to protect the cells from cold-induced damage.
“We use electric pulses because electric pulses will open pores inside the cells and then these pores are kind of gates that allow this solution to get also inside,” says Federico Gomez, associate professor of food technology at Lund University.
The treated vegetables are then stored in a freezer. Once defrosted, the researchers say they look and taste as though they have just been harvested. Tests have so far applied to vegetables frozen for up to a month.
“The key feature of the method is that we keep the cells alive after thawing. It means that all the fresh-like characteristics will be intact. So the consumer would probably not notice the difference (between our vegetables and fresh vegetables),” says Federico Gomez.
Along with spinach, the team at Lund University has also successfully given parsnips and strawberries the eternal youth treatment. Potatoes were less successful because of their density. The team hopes that trehalose-treated frozen vegetables will be available for sale within a year.