Grape berry coatings of lemongrass oil-incorporating nanoemulsion

Grape berries are highly perishable and vulnerable to contamination with foodborne pathogens. Nanoemulsions of lemongrass oil (LO) were developed for coating of grape berries (Vitis labruscana Bailey) to improve the shelf life and microbiological safety. Vortex mixing, high-shear probe mixing, and dynamic high pressure (DHP) processing were tested as methods of incorporating LO into a carnauba-based solution (0.5-4.0 g/100 g LO). The coating solutions produced by DHP demonstrated the highest emulsion stability and resulted in uniform and continuous coatings on grape berries. The coating on the berries with 3.0 g/100 g LO initially inhibited Salmonella typhimurium and Escherichia coli O157:H7 inoculated on the berries by more than 3.2 and 2.6 log CFU/g, respectively. The coatings did not significantly alter the flavor of the berries and improved their glossiness. Antimicrobial effects against S. typhimurium and E. coli O157:H7 were exhibited during storage at 4 and 25 °C for 28 days. The coatings were also effective on reducing losses of weight, firmness, phenolic compounds, and antioxidant activity and delaying increases in total anthocyanin concentration in the berries. The LO-nanoemulsion coatings have demonstrated the potential to inhibit foodborne pathogen contamination of grape berries, and prolong their shelf life.