The Application of Dill Essential Oil Combined with Zinc Oxide Nanoparticles in Active Coating Based on Carboxy Methyl Cellulose in order to Extend the Shelf Life of Shrimp under Refrigeration Condition

Shrimp among the sea food has the highest commercial demand universally. Due to biochemical, microbiological and physical spoilage after receiving from sea, it has a short shelf life. The object of this research is to improve the shelf life of shrimp caught from the sea. Active edible Carboxy Methyl Cellulose (CMC)-based coating containing Zinc Oxide nanoparticles (0.03%) and dill essential oil with 0, 1, 2, 3 and 4% levels as biopreservative were prepared to extend the shelf life of shrimp during 12 days of storage at 4 ºC. Using active edible CMC-based coating led to the reduction of pH changes in shrimp coated samples during storage time, therefore coating containing ZnO nanoparticles and 4% dill essential oil were most effective in increasing storage time significantly (p<0.05) and increased TVB-N content until the end of the 12 days but using ZnO nanoparticles and increasing the concentration of dill essential oil from 0 up to 4% resulted in a significant (p<0.05) decrease in TVB-N content. Although incorporation of the dill essential oil compared to control significantly (p<0.05) decreased the L* and increased the b values during storage time and the treated samples with a higher levels of the essential oil had less color changes. However, extending the storage time significantly (p<0.05) increases the b and reduces the L* values of shrimp samples. Increasing the storage time caused a significant decrease (p<0.05) in hardness of the shrimp samples but the use of nanoparticles and the essential oil reduces the process of softening. Total aerobic bacteria, E.coli and coagulase-positive Staphylococcus aureus counts showed that number of microorganisms was dependent on the presence of nanoparticles and the essential oil dosage used for treatment as well as storage time. Using high levels of the essential oil led to an increase (p<0.05) in sensory parameter scores significantly, therefore the treatment containing 3% dill essential oil had the highest acceptability score. The use of 3% dill essential oil as biopreservative along with ZnO nanoparticles in the structure of active edible CMC-based coating is recommended for the preservation of shrimp at 4 ºC.