Comparison of effectiveness of edible coatings using emulsions containing lemongrass oil of different size droplets on grape berry safety and preservation

- Dynamic high pressure process produces stable lemongrass oil-chitosan nanoemulsion.
- Nano-coating preserves grapes longer than conventional emulsion coating.
- Nano-coating improves microbiological safety against Salmonella on grape berries.
- Nano-coating minimizes differences in sensory attributes compared with fresh grapes.

Effects of lemongrass oil (LO) droplet size in the LO/chitosan emulsion on the emulsion's coating effectiveness in improving microbiological safety and preserving grape berries (Vitis vinifera L. × V. labruscana Bailey) were investigated. LO was homogenized with a chitosan solution (1 g/100 g) and Tween 20 (0.25 g/100 g) by high shear mixing (HSM; 10,000 rpm, 1 min) or dynamic high pressure processing (DHP; 103-172 MPa, 1-3 passes), forming LO coating emulsions. The particle sizes of the HSM and DHP emulsions were 461.9-632.6 nm and 204.2-378.8 nm, respectively. DHP emulsions were more stable than HSM emulsions. Compared with the HSM emulsion, the DHP emulsion coating resulted in higher initial inhibition of Salmonella typhimurium; greater growth inhibition of total mesophilic aerobes, yeasts, and molds; and retention of color, total soluble solid content, and antioxidant activity during storage at 25 °C (P < 0.05). The sensory results suggest that the DHP emulsion minimized differences in sensory attributes compared with uncoated grape berries more effectively than did the HSM emulsion coating. The nanoemulsion coating with smaller LO droplets demonstrated greater efficiency in increasing microbial safety against Salmonella and preserving grape berries, compared with the coating with larger droplets.