Edible Spider Silk Coating Keeps Fruit Fresh Without Refrigeration

A dip in a protein solution of water and silk fibroin can preserve perishable foods, according to new research. Inacio Peres/EyeEm/Getty Images

A new technological development may mean a significantly longer life for fruits and vegetables. Biomedical engineers at Tufts University have shown that coating fruit in an odorless, edible, water-based silk solution can keep fruit fresh for more than a week without refrigeration.

But this isn't just about extending the life of that banana on your shelf you keep telling yourself you should eat any day now. As food travels along the supply chain from farm to consumer, according to the UN's Food and Agriculture Organization, the world loses half of the fruit and vegetable crops grown for human consumption.

"Food waste has an impact on food quality and safety," the authors write, "representing a loss of economic value and resources, and, a hindrance to economic development."

The researchers published their findings today in the journal Scientific Reports, outlining how the silk fibroin, a protein essential to silk and spiderwebs and similar to collagen, can be suspended in water to create a 1 percent protein solution. Dissolvable film made from silk fibroin has previously been used to create implantable brain electrodes and as adhesive, edible sensors to monitor fruit ripening and cheese aging.

The scientists tested with strawberries — one of the hardest fruits to keep fresh — and bananas in their study, dipping the perishable fruits into the solution to provide a nearly invisible, coating 27 to 35 microns thick — that's just one one-thousandth of an inch. This coating reduced the fruit's cell respiration rate by regulating the natural flow of oxygen and carbon dioxide, and slowed the rate at which water in the fruit evaporated — essentially, slowing down the decomposition process

Current coating methods of fruit preservation include applying layers of polysaccharides, proteins, resins, lipids and combinations of different materials, all with different properties. The scientists say that, in addition to reducing food waste, this development using silk fibroin would mitigate some of the drawbacks of other forms of coating, providing a substance that's biodegradable, anti-allergenic, antibacterial and antifungal.

The coating process resulted in no discernible change in the fruit's texture, although the study notes that the scientists didn't test for any change in taste.

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