Ultra-Thin Silk Coatings – An Ideal Way to Preserve Fresh Fruit

As a consumer I so look forward to the fresh fruits and vegetables available to us in the summer – BUT the downside is that they usually deteriorate if not used rather quickly.  Even in the stores you see fruits and vegetables going bad prior to sale or disposal.  Can you imagine the global dollar loss associated with perishable fruits and vegetables? It must be astounding.

A recent report published in the May 6 issue of Scientific Reports describes work conducted by Tufts University biomedical engineers. The researchers have demonstrated that fruits can stay fresh for more than a week without refrigeration if coated with an ultra-thin silk solution. The coating is made from a naturally derived material and a water-based manufacturing process.

The protein fiber of silk is composed mainly of fibroin, which is insoluble and has the ability to stabilize and protect materials, yet be biocompatible and biodegradable.  Tests on fresh strawberries showed that, even after seven days without refrigeration, coated berries were still firm and juicy and did not show signs of decay.  Apparently the edible silk coating slows fruit respiration and makes strawberries less permeable to carbon dioxide and oxygen.

Tests were also conducted on bananas which do continue to ripen when picked.  In fact they often ripen way too quickly when you bring them home.  Tests showed that the silk coating prolonged the freshness of the fruit by slowing fruit respiration, extending fruit firmness and preventing decay.

This lab has also developed a biocompatible, biodegradable silk-based dental implant coating capable of withstanding the mechanical stresses imparted during implant replacement.  They have just recently shown that silk can be used to preserve blood samples at room or body temperatures.

It should be noted that the David Kaplan lab at Tufts focuses on biopolymer engineering to understand structure-function relationships, with emphasis on studies related to self-assembly, biomaterials engineering, tissue engineering and regenerative medicine. The studies include a variety of structural proteins, including collagens, elastins, resilins and silks.

The lab has pioneered the study of silk-based biomaterials in regenerative medicine, starting from fundamental studies of the biochemistry, molecular biology, and biophysical features to the impact on stem cell functions and complex tissue formation. The result has been the emergence of silk as a new option in the degradable polymer field with excellent biocompatibility, new fundamental understanding of control of water to regulate structure and properties, and new tissue-specific outcomes with silk as scaffolding in gel, fiber, film or sponge formats. Studies are also focused on tissue engineering and regenerative medicine with the use of complex 3D tissue co-culture systems to establish and study human tissues in the laboratory and in animal systems. These systems are also used to study diseases associated with brain, intestine, kidney, obesity, diabetes and cancers, including for therapeutic screening.