Okra or ladies’ fingers is a local vegetable commonly grown in Oman. It is one of the most heat and drought resistant species in the world. Okra is commonly used to cook different dishes in different cuisines worldwide. Okra pods contain up to 90% of water. After okra are harvested, it has a limited shelf life. During storage okra loses its water and became quickly rotten by fungi and bacteria.
Packaging plays a critical role in food safety and quality. Packaging acts as a barrier that protects the food from the outer environmental conditions. Most of vegetables are packed in flexible plastic film. This film does not have antimicrobial properties and does not prevent growth of bacteria and fungi. Food packaging with antimicrobial properties has received attention due to the ability to arrest or delay microbiological decay of food products. In antimicrobial packaging materials, antimicrobial substances are loaded in the packaging system to reduce the risk of contamination by pathogens.
Dr. Laila Al-Naamani, a researcher from the department of Marine Science and Fisheries, Sultan Qaboos University, invented a novel nanocomposite antimicrobial packaging. Her work was supervised by Dr. Sergey Dobretsov from the Centre of Excellence in Marine Biotechnology and Prof. Joydeep Dutta from the Royal Institute of Technology KTH, Sweden. Their discovery entitled “Nanocomposite Zinc Oxide-Chitosan Coatings on Polyethylene Films for Extending Storage Life of Okra (Abelmoschus esculentus)” was recently published in a peer review high impact factor Nanomaterials journal. This study was conducted together with researchers from the Centre of Nanaotechnology, Sultan Qaboos University and in collaboration with Food and Water Laboratory center in the Ministry of Regional Municipalities and Water Resources.
Nanotechnology is manipulation of matter on an atomic, molecular and supramolecular level. Nanotechnology allows to create new materials with novel chemical and physical properties. During the investigation, Dr. Al-Naamani incorporated zinc oxide nanoparticles with size of 100 nanometers into chitosan and coated polyethylene films to fabricate antimicrobial packaging. Chitosan is a linear polysaccharide produced from chitin. Chitin is a major component of shrimps and crabs’ shells and usually is discarded with the waste.
The researchers tested the efficiency of the nanocomposite zinc oxide-chitosan antimicrobial coating for the preservation of vegetables. Locally grown okra pods were storied in the package with or without novel nanocomposite coating. The results demonstrated that the nanocomposite coating reduced the number of bacteria by more than 60% compared to orka stored without it. Moreover, the nanocomposite coating showed a 2-fold reduction in fungal concentrations in okra compare to the samples stored in package with chitosan only. Additionally, the novel nanocoposite coating helped to maintain moisture and physical and chemical properties of storied okra. This work proved that the chitosan-ZnO nanocomposite coating not only maintains the quality of the packed okra but also, retards growth of microbes significantly. Overall, this study demonstrated that chitosan-ZnO nanocomposite coating can be used as a potential coating material for active food packaging applications.