Improving the Microbiological Safety of Candy Apples and Shredded Lettuce Through Applying Sequential Intervention Steps

Kayla Murray
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University of Guelph

The following reports on the efficacy of sequential treatments to decontaminate fresh produce using candy apples and shredded lettuce as model systems. A forced air ozone treatment was developed to treat whole apples and lettuce heads. By using a combination of laboratory and pilot scale studies, the treatment time, air flow and ozone concentration was optimized to support a 1.90-2.40 log CFU of target bacteria. A further process based on advanced oxidation process (AOP) was developed using a combination of UV-C, hydrogen peroxide and ozone generated by a lamp emitting at a wavelength of 174nm. From optimization studies it was found that using a combination of UV-C and 6% hydrogen peroxide reduced Listeria monocytogenes by 0.86 log CFU. By using a combination of treatments it was possible to achieve a >5 log cfu reduction of target pathogens. The technologies developed during this study provides preventive controls that can be applied in post-harvest fresh produce processing.

Candy apples, Shredded lettuce, Microbiological safety, Decontaminate fresh produce, UV-C, Hydrogen peroxide