Photo Credit: Hadas Parush/Flash90
Strawberries on display at the Mahane Yehuda Market in Jerusalem, November 26, 2019.

Whether in the refrigerator or on the kitchen counter, fruits and vegetables often spoil before we’ve even had a chance to eat them. Extending their shelf life has long challenged science.

At the Department of Chemistry at Bar-Ilan University, PhD student Belal Abu Salha has developed a process of coating fruits and veggies with edible nanoparticles using sonochemistry. Abu Salha’s research began at his family’s strawberry nursery in the Golan Heights in northern Israel, where he often wondered how he could prolong the freshness of the fruit from the moment picked until the moment eaten.

Ph.D. student Belal Abu Salha. / Courtesy of Bar-Ilan University

“I used sonication, a process of applying an ultra-sound energy in a liquid, to develop nano-coated particles from chitosan. Chitosan is a natural substance derived from polymers such as chitin, polysaccharides, and proteins,” explains Abu Salha. “Sonochemistry allows the chitosan particles to embed into the surface of the fruit and coat it quickly and efficiently, and the coating significantly decreases the damage to the fruit caused by fungi and bacteria.”

The process can be used as a safe substitute for current methods to preserve produce. The coating significantly decreases damage caused by bacteria and fungi, thereby extending shelf life and preserving fresh taste and quality. Moreover, chitosan is environmentally friendly and biodegradable.

Prof. Aharon Gedanken, from the Chemistry Department at Bar-Ilan University, developed the sonication method and advised Abu Shilha’s research. “When you bombard a liquid solution with high-frequency sound waves, in a process called ultra-sonication, the solution swirls rapidly and masses of microscopic bubbles are formed that collapse into themselves. When the collapse occurs near a solid surface, like a strawberry or even a millimeter grain of material, liquid streams move to the surface of the solid at a very high speed and toss the particles from the solution onto the surface at enormous speeds. The particles are embedded in the solid and cannot be removed, even by washing it. In this way, it’s possible to assign a solid with properties it didn’t have in the first place – antibacterial properties or resistance properties, for example. This is how antibacterial substances can be embedded in fruits and vegetables or any other material.”

During the research process, the chitosan solution underwent a sonochemical process, and the sound waves caused the creation of edible nanoparticles with antibacterial properties that were embedded on the surface of the strawberry, according to Abu Salha. “Then I tested the antibacterial activity of the strawberry and the physical and chemical properties such as the sugar level in the fruit, acidity, and spoilage rate. I discovered that the shelf life of the strawberries treated with edible nanoparticles of chitosan was extended by 15 days!”

Abu Salha’s discovery has tremendous implications for his family’s strawberry business in the Golan. Through sonochemistry and its innovative approaches to green chemistry, this research facilitates the discovery of easy, efficient, and environmentally friendly solutions and their application in the food preservation industry. Abu Salha’s innovative approach will allow for the preservation of fruits, vegetables, and fresh foods for a longer period and prevent fungi and bacteria from affecting their quality.


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