Electrostatic spraying of produce using organic acids appears to provide effective protection against E. coli, according to new research published in the Journal of Food Science.
Electrostatic spraying creates a naturally charged attraction between the sprayed particles and the targeted surface-whether it’s a wall being painted or a plant leaf being chemically protected from pests or pathogens. The “mutual attraction” means that the droplets of liquid coat leaves evenly and don’t drip onto the ground like conventional sprays do.
In the new study, researchers at the University of Arkansas used an electrostatic spray technique to evenly coat E. coli-treated spinach and lettuce samples with grape seed extract and with malic, tartaric, and lactic acid, alone and in combinations. They found that the organic antimicrobials had a significant effect: Lactic acid and malic acid in combination, for example, yielded a 2.1 to 4.0 log CFU/g reduction of E. coli between days one and 14 on spinach and 1.1 to 2.5 log CFU/g reduction on lettuce.
By comparison, a spray of phosphoric acid and pH controls, applied using deionized water, yielded only a 1.1 to 2.1 log CFU/g inhibition of E. coli on spinach during the 14-d storage. Lead researcher Navam Hettiarachchy, PhD, a professor in the Integrated Protein, Nutraceuticals and Food Safety Program within the Department of Food Science and the Institute of Food Science and Engineering at the University of Arkansas in Fayetteville, said electrostatic sprayers achieve four to ten times better coverage than conventional sprayers.
Electrostatic spraying has become popular in pesticide and fertilizer application, but it has taken longer to catch on as a technique for decontaminating produce from pathogens.
“When you’re spraying these solutions directly on food products, you need to think about freshness and optimize a lot of conditions that you don’t have to worry about with non-food items,” explained Dr. Hettiarachchy. “Unlike with pesticides, you need to optimize conditions to suit the surface area for wider coverage-but electrostatic spraying in food safety will soon be catching up.”