Half of the world's fruit and vegetable crops are lost during the food supply chain, mostly due to premature deterioration of these perishable foods, according to the Food and Agriculture Organisation (FAO) of the United Nations.
Your favourite strawberries and bananas can stay fresh for more than a week without refrigeration if they are coated in a thin, odourless, biocompatible silk solution, says a study. Silk's unique crystalline structure makes it one of nature's toughest materials. Fibroin, an insoluble protein found in silk, has a remarkable ability to stabilise and protect other materials while being fully biocompatible and biodegradable.
For the study, the researchers dipped freshly picked strawberries in a solution of one percent silk fibroin protein. The coating process was repeated up to four times. The silk fibroin-coated fruits were then treated for varying amounts of time with water vapour under vacuum (water annealed) to create varying percentages of crystalline beta-sheets in the coating.
"The beta-sheet content of the edible silk fibroin coatings made the strawberries less permeable to carbon dioxide and oxygen. We saw a statistically significant delay in the decay of the fruit," said senior study author Fiorenzo Omenetto, professor at Tufts University in Massachusetts, US. Similar experiments were performed on bananas, which, unlike strawberries, are able to ripen after they are harvested.
The silk coating decreased the bananas' ripening rate compared with uncoated controls and added firmness to the fruit by preventing softening of the peel. The findings were published in the journal Scientific Reports.