Edible eco-friendly coating keeps fruit fresh without a fridge for more than a week

Bananas without a protective coating and coated

Bioengineers from Tufts University have demonstrated a new coating for vegetables and fruits, keeping them fresh outside the refrigerator for more than a week. The coating does not contain any plastic, biodegradable, and moreover, edible. The material of the protective coating is fibroin, the protein that underlies the cobweb and cocoons of insects, in particular, silk.

According to the Food and Agriculture Organization of the United Nations, half of the vegetables and fruits collected in the fields and orchards do not reach the consumer, spoiling on the way. On the other hand, the use of plastic for packaging products, although justified in terms of their preservation, is completely harmful to the environment. By some estimates , by 2050 there will be more plastic in the oceans than fish.

The coating on the basis of fibroin is almost invisible, odorless, and the process of its production is based on water. The unique properties of fibroin allow it to stabilize as a coating and protect other surfaces, while remaining biodegradable and environmentally friendly.
')
The researchers tested the coating on bananas and strawberries. The fruits were dipped into a 1% fibroin solution several times. To enhance the coating, the fruits were then exposed to water vapor in a vacuum chamber — at this time crystalline beta sheets appeared (one form of the regular secondary structure of proteins). Depending on the processing time, the number of beta sheets in the coating varied.


In the first column, raw strawberries, in the second - with a coating containing a small amount of beta sheets, in the third - with a large number of beta sheets

Then the fruits were stored at room temperature. After a week, the strawberry coated with fibroin was juicy and elastic, and the usual lost moisture and color. The coating prevented water loss and slowed down rotting.

“The content of beta sheets in the edible fibroin coating made strawberries less permeable to oxygen and carbon dioxide. We observed a statistically significant slowdown in decay processes, ”writes the main author of the study, Fiorenzo Omenetto [Fiorenzo G. Omenetto].

A similar experiment with bananas, which are able to ripen even after assembly, showed that the coating significantly slows their ripening and retains its elasticity even after 9 days of storage. The texture of the fruit does not suffer. True, scientists have not yet tested how much the taste of the fruit changes.