Italian National Agency for New Technologies, Energy and Sustainable Economic Development
Agri-food: New organic layer to make fruit and vegetables last longer
ENEA has developed a transparent coating made of grapefruit and apple extracts to be applied on fresh produce.
A new low-cost, anti-mold coating to be applied directly on fruit and vegetables to preserve their quality and nutritional properties for up to ten days, which ENEA has developed jointly with the University of Salerno (Department of Industrial Engineering), it appeared in the journal Nanomaterials.
It is an edible, odorless and tasteless layer, made of pectine-based nanocomposites -extracted from apple peel and grapefruit seed oil, which has antimicrobial properties, encapsulated in aluminum-silicate nanotubes. To test the food bio-coating, the team chose the strawberry, which is a very perishable fruit; the results were very encouraging, especially in the case of the protective film with the highest concentration of grapefruit seed oil, which proved to be very effective in conservation.
“We soaked the strawberries for two minutes in three different formulations with different content of grapefruit seed oil. Then we left them at room temperature for ten days, with a 60% humidity. On the tenth day, the fruits treated with the highest concentration of essential oil were still intact and edible, while those without bio-coating, after only two days, were already rotten and completely covered with mold", explained Loredana Tammaro, researcher at the ENEA Nanomaterials and Devices Laboratory at the Portici Research Center.
Pectin is a natural thickener extracted from apples and citrus fruits, also used in the food industry for its 'film-forming ability [1]’. “Films based on pure pectin, however, promote microbial growth, since they are used as a carbon source by fungi and bacteria. Hence the idea of making this natural polymer 'active' with antimicrobial agents, such as grapefruit seed oil, to obtain sustainable, health-safe and low-cost materials, suitable for food packaging and storage”, continued the ENEA researcher.
Essential oils, besides being natural sources of fragrance compunds, have interesting antimicrobial properties against some pathogens and food contaminants. Of all the essential oils, the one from grapefruit seeds has proven to have antifungal, parasiticidal, antibacterial, antioxidant and antitumor properties and exhibits microbial growth inhibition against Gram-positive and Gram-negative bacteria. "The use of pectin coupled with grapefruit seed oil encapsulated in halloysite nanotubes - a clay based on aluminum silicate - resulted in an improvement in the mechanical performance of the biodegradable film (increase in the elastic modulus, stress at break, and deformation at break) and a reduction in water absorption, compared to pure pectin film ”, pointed out the ENEA researcher.
Encapsulating these substances in nano-containers to preserve their stability has been shown to be an encouraging strategy. During the tests, the release, up to 21 days, of linoleic acid, the main component of grapefruit seed oil, was detected. "This demonstrates the possibility to act on the time of release of active molecules thanks to the use of halloysite nanotubes, which have aroused considerable interest because they are cheap eco-materials abundantly available in nature", said Loredana Tammaro.
For more information:
Loredana Tammaro, ENEA - Nanomaterials and Devices Laboratory
The article on Nanomaterials is available at: https://doi.org/10.3390/nano12081265