Purpose: As the first step in development of a process that would combine mechanical disruption and spray technology, this study evaluated using abrasive mechanical disruption (abrasive-particulate blasting) and air-assisted electrostatic-induction spray sanitizer application, in tandem, to remove biofilms from stainless steel surfaces.
Methods: An abrasive blasting chamber was fabricated so the abrasive blast stream was directed at stainless steel coupons containing Listeria monocytogenes biofilms. Coupons were positioned at a 60° angle horizontal to the spray and at distances of 8.9 and 24.1 cm from the nozzle. Each coupon was blasted with the abrasive (425-710 μm; 317 g/min) for 10 sec at 40 psi. Then levulinic acid and sodium dodecyl sulfate (SDS) sanitizer was applied so equal quantities of active ingredient were dispensed using either an air-assisted electrostatic nozzle with droplet charging ON (~ -7 mC/kg charge-to-mass) or with charging OFF or with a conventional hydraulic nozzle. For accurate spray application, nozzles were attached to a repeatable robotic arm. The methods were evaluated for the reduction in the population of colony forming units of Listeria monocytogenespreviously inoculated onto the stainless steel surfaces.
Results: Abrasive mechanical disruption at a nozzle distance of 24.1 cm from the stainless steel surface combined with air-assisted charged spray worked best and reduced the number of biofilm cells by 5.28 logs CFU when using a sanitizer comprised of 6% levulinic acid and 0.6% SDS.
Significance: Bacterial biofilms present significant obstacles in food processing environments. Development of a process that can deliver abrasive mechanical disruption and low-volume electrostatic application of sanitizer spray may provide an effective means for biofilm control.