Abstract:
This research developed foam-mat freeze-dried clove essential oil nanoemulsion (FFD-CN) for inhibiting food spoilage microorganisms. This research comprised three parts. Firstly, the fabrication of clove essential oil nanoemulsion (CN) was optimized. The characteristics including particle size, polydispersity index (PDI), Zeta-potential, and viscosity of the fabricated nanoemulsions were observed. The optimal CN having a droplet size of 30.76 nm, PDI of 0.179, Zeta-potential of -50.01 mV, and viscosity of 7.81 cP was achieved at 1% v/v clove oil and 3% v/v Tween® 80 concentration and 10,000 psi operating pressure. The CN exhibited stability against particle aggregation and phase separation throughout storage. Moreover, the CN exhibited better antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa when compared to clove oil. Secondary, the foam-mat freeze-drying (FFD) technique was used to maintain stability and antimicrobial activity of CN. The optimal condition was found at 3% (v/v) of foaming agent (MethocelTM), 60 °C drying temperature, and 72 h drying time. The obtained FFD-CN had the droplet size of 26.14 nm, PDI of 0.193, water activity (aw) of 0.273, solubility of 88.71%, and viscosity of 12.85 cP. The FFD-CN exhibited good stability and maintained antimicrobial activity, as analyzed using minimum inhibitory concentration (MIC), against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus better than CN. Lastly, the FFD-CN was investigated for its efficiency to maintain the quality of whiteleg shrimp during chilled storage (4 ± 2 °C) in comparison to CN and distilled water (control). The CN and FFD-CN were found to be effective in inhibiting the growth of bacteria in whiteleg shrimp. FFD-CN was more effective than CN in delaying the changes in trimethylamine (TMA), total volatile basic nitrogen (TVB-N), total viable count (TVC), texture, color, and pH. The analysis of volatile compounds of all samples showed that FFD-CN could maintain a higher concentration of eugenol than CN and clove oil. The results also suggested that Control, CN, and FFD-CN treated shrimp had the shelf life of 6, 8, and 10 days, respectively. The FFD-CN can effectively be used as a natural preservative for maintaining the quality and shelf life of whiteleg shrimp.
