New Electrostatic salad spraying technique shows ‘efficacy’ against E.coli – study

In recent years, the authors noted, a significant number of US E.coli outbreaks have been linked to fresh and fresh-cut vegetables such as spinach, lettuce, alfalfa sprouts, hamburger or salami meats (Caprioli and others 2005).

Conventional sanitation methods for fresh produce involve water, chlorine, peroxyacetic acid, acidified sodium chlorite, hydrogen peroxide, ozone or brush and spray washers, they wrote. However, the rising prevalence of E. coli outbreaks suggests that these strategies may not be fully effective.

Efficiency of application​

Writing in the Journal of Food Science, ​the study authors Vijayalakshmi Ganesh, Navam S. Hettiarachchy, Carl L. Griffis, Elizabeth M. Martin, and Steven C. Ricke criticised current cleaning methods.

“Many of these methods and commercial/washing spraying equipment lack efficiency of application, which may lead to run-off or uneven distribution of the antimicrobials,”​ they wrote.

Therefore, Ganesh et al. set out to test the theory that using electrostatic spraying to evenly distribute natural antimicrobials could be a more efficient and effective solution.

Dr. Navam Hettiarachchy, co-author and professor at the Department of Food Science & Institute of Food Science and Engineering, at the University of Arkansas, told Foodproductiondaily.com:

“Electrostatic sprayers apply solutions more effectively than conventional sprayers by applying electrical charge to liquid droplets as they are sprayed through a nozzle.”​

He added: “The charge causes droplets to wrap around objects, and even overcome gravity, resulting in thorough, even coverage of the target, which conventional methods cannot achieve.”​

Lower public health burden​

The researchers also examined the effects of organic antimicrobials as a more environmentally and consumer-friendly alternative to harsher disinfection treatments.

Spinach and lettuce samples were sprayed electrostatically with the organic acids malic, tartaric and lactic acid and grape seed extract alone and in combinations, and for comparison, with phosphoric acid and pH controls with deionised water.

During a 14-day storage period, malic acid/lactic acid and malic acid/lactic acid/grape seed extract combinations had the greatest decontaminating effect; whilst inorganic treatments showed promising effects, these were lower in comparison and compromised the colour of the produce.

“Our findings demonstrated the efficacy of electrostatic spraying of malic acid, lactic acid and grape seed extract on fresh produce to improve the safety and lower the public health burden linked to produce contamination,”​ the researchers wrote.

Researcher’s high hopes​

Although it is currently used in agriculture for pesticide and fertiliser application, electrostatic technology isn’t in commercial use for fresh produce sanitation.

“Reasons could be the cost of the electrostatic sprayer units, the need to clean the nozzles well after use and the need for enclosed spaces for safety and efficacy,”​ Hettiarachchy said.

“But this is an emerging technology to be used in food production and hopefully the food industry will use it,”​ he added.

Title:​ ‘Electrostatic spraying of food-grade organic and inorganic acids and plant extracts to decontaminate Escherichia coli O157:H7 on spinach and iceberg lettuce’

Authors:​ V.Ganesh, N.S Hettiarachchy, C.L Griffis, E.M Martin, S.C Ricke

Source:​ Journal of Food Science​ (Volume 77, Issue 7, pages M391–M396, July 2012) doi: 10.1111/j.1750-3841.2012.02719.x​