P3-87 Forced Air-Ozone Reactor Combined with Sequential Advanced Oxidative Process to Inactivate Listeria monocytogenes on Apples Destined for Candy Apple Production

Wednesday, July 12, 2017
Exhibit Hall (Tampa Convention Center)
Kayla Murray , University of Guelph , Guelph , Canada
Fan Wu , University of Guelph , Guelph , Canada
Keith Warriner , University of Guelph , Guelph , Canada
Introduction: In 2014 there was an outbreak of listeriosis associated with contaminated candy apples, thereby requiring a preventative control intervention to be applied. Simple washing apples in sanitizing solutions is limited and in any event not preferred given that fruit requires to be dried to ensure adhesion of the candy layer. Therefore, alternative, aqueous-free, decontamination method(s) are required.

Purpose: This study was conducted to develop an ozone based treatment followed by advanced oxidative process (AOP) to inactivate L. monocytogenes introduced onto and into apples destined for candy apple production and to determine the fate of L. monocytogenes during posttreatment storage.

Methods: A forced air ozone reactor was constructed that introduced antimicrobial gas through an airstream into a column of apples that had been surface and subsurface inoculated with L. monocytogenes. The AOP reactor combined hydrogen peroxide mist in a chamber illuminated with ultraviolet light at 254 nm and ozone generation at 174 nm. The optimized treatments were applied to decontaminate apples that were used to prepare candied apples. The fate of L. monocytogenes on the candied apples during storage at 4 or 22°C was assessed.

Results: The ozone treatment optimized with respect to air flow and treatment time resulted in 1.90 to 2.40 log CFU reduction of target bacteria throughout the apple bed, but negligible decrease in subsurface populations. AOP, using 6% hydrogen peroxide vapor introduced at 48°C, and ultraviolet illumination for 30 s supported a four log CFU reduction of Listeria on the surface and 0.86 log CFU of internal populations. When combined in a sequential process, residual levels did not undergo outgrowth in the produced candy apples stored at 4 or 22°C.

Significance: A sequential process based on ozone and AOP provided an effective prevention control intervention for apples and could be extended to other fresh produce.