Silk coating makes for fresher fruit

Fruit treated with the coating retains moisture longer, and ripens slower(Credit: Sunmoon/C.C. 2.0)

How often do you end up throwing out fruit that spoiled before you could eat it? Well, it may soon be happening a lot less, thanks to a silk-based coating being developed at Tufts University in Massachusetts. Strawberries treated with the substance remained fresh and juicy for up to a week without refrigeration – unlike their untreated counterparts.

Silk is regarded as being one of nature's strongest materials, thanks mainly to an insoluble protein within it. Called fibroin, that protein is known for its ability to protect other materials when applied to them. It's also biocompatible, biodegradable, and otherwise safe to consume.

In the Tufts study, freshly-picked strawberries were first dipped repeatedly in a solution of 1 percent fibroin. They were then treated with water vapor under vacuum, in a process known as water annealing, to create crystalline sheets in the coating. The longer that they were subjected to that process, the thicker the coating became.

Even at a thickness of up to 35 microns, that coating was still virtually invisible to the naked eye, yet nonetheless substantial enough to drastically slow down fruit respiration and thus prevent decay. Not only did it keep strawberries edible for seven days when stored at room temperature, but it also slowed the ripening rate of bananas when applied to the outside of their peels.

It should be noted that the taste of the treated fruit was not assessed. Should that be an issue, previous studies have also had luck with fruit coatings made from pectin, and from chitosan derived from shrimp shells.

A paper on the Tufts research was published this Friday in the journal Scientific Reports.

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