Study Finds Edible Silk May Slow Fruit Spoilage

     (CN) — Feeding a global population of more than 7 billion people is challenging given that roughly half of all fruit and vegetable crops deteriorate along the food supply chain, according to the United Nations’ Food and Agriculture Organization.
     But researchers at Tufts University might have a solution: fruits could stay fresh for over a week without refrigeration if they are protected by a silk solution that is so thin it is barely visible.
     The Tufts researchers published their findings May 6 in the journal Scientific Reports.
     Silk is one of nature’s toughest materials, largely due to the insoluble protein fibroin. Fibroin protects and stabilizes other materials and is completely biodegradable and biocompatible.
     In the study, the researchers dipped freshly picked strawberries in a solution of 1 percent silk fibroin protein, coating it up four times. The strawberries were then treated for various lengths of time with water vapor under vacuum in order to create varying percentages of crystalline beta-sheets in the coating. The percentage of beta-sheets increased the longer the fruit was exposed, leading to more robust fibroin coating, and the strawberries were stored at room temperature afterward.
     The coating was 27 to 35 microns thick, or about two-thousandths of a centimeter. The researchers then compared the coated berries over time with untreated fruits.
     At seven days, strawberries coated with the higher beta-sheet silk remained ripe, while uncoated strawberries were discolored and dehydrated. Tests revealed that silk coating extended the freshness of the strawberries by slowing fruit respiration, preventing decay and extending fruit firmness.
     “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,” Fiorenzo G. Omenetto, senior study author and professor in the department of biomedical engineering at Tufts University, said in a statement.
     The team also performed experiments on bananas, which unlike strawberries ripen after they are harvested.
     The silk coating slowed the bananas’ ripening rate compared to uncoated controls, while also adding firmness and preventing the peel from softening.
     “Various therapeutic agents could be easily added to the water-based silk solution used for the coatings, so we could potentially both preserve and add therapeutic function to consumable goods without the need for complex chemistries,” Benedetto Marelli, a study author, said in the statement.

%d bloggers like this: